Now the tradition the church at Rome was following did exist, but it wasnt the tradition of the Apostles as we can see from the changes. But there was a tradition, the corruption from the Gnostic sect had brought about what is called the Disciplina Arcani or Discipline of the Secret or Discipline of the Arcane, which was a restriction imposing silence upon Christians with respect to their rites and doctrines. It was a theological term used to describe the custom which came in and prevailed in the church, whereby knowledge of the more 'intimate mysteries' of the Christian religion was carefully kept from non-Christians and even from those who were undergoing instruction in the faith. The church in the early stages picked up pagan oral teachings from Greek and Hellenistic sources which formed the basis of this secret oral tradition, which in the 4th century came to be called the disciplina arcani. It is believe that it contained liturgical details and certain other pagan traditions which remain a part of Christianity, for example, the doctrine of Transubstantiation is thought to have been a part of this.
There are many sources that point out the origins of the corruption....
...the "temples, incense, oil lamps, votive offerings, holy water, Holidays, and seasons of devotion, processions, blessings of the fields, sacerdotal vestments, the tonsure (of priests, munks and nuns), images, and statues... are all of PAGAN ORIGIN." -The Development of the Christian Religion Cardinal Newman p.359
The penetration of the religion of Babylon became so general and well known that Rome was called the "New Babylon." -Faith of our fathers 1917 ed. Cardinal Gibbons, p. 106
"Confiding then in the power of Christianity to resist the infection of evil, and to transmute the instruments and appendages of demon worship to an evangelical use... the rulers of the church from early times were prepared should occasion arise, to adopt, or imitate, or sanction the existing rites and customs of the populace." -Development of Christian Doctrine, Cardinal Newman. p. 372
Cardinal Newman lists many examples of things of "pagan origin" which the papacy brought into the church "in order to recommend the new religion to the heathen: "in order to recommend the new religion to the heathen:" "The use of temples, and these dedicated to particular saints, and ornamented on occasions with branches of trees; incense, lamps, and candles; holy water; asylums [hermitages, monasteries and convents]; [pagan] holy-days, processions, sacerdotal vestments, the tonsure, the ring in marriage, turning to the East, images, . . . and the Kyrie Eleison."--Cardinal J. H. Newman, An Essay on the Development of Christian Doctrine, 1920 edition, p.373 [Roman Catholic].
"The [Catholic] Church took the pagan philosophy and made it the buckler of faith against the heathen. She took the pagan Roman Pantheon, temple of all the gods, and made it sacred to all the martyrs; so it stands to this day. She took the pagan Sunday and made it the Christian Sunday. She took the pagan Easter and made it the feast we celebrate during this season . . . The Sun was a foremost god with heathendom . . . The sun has worshipers at this hour in Persia and other lands . . . Hence the Church would seem to say, 'Keep that old pagan name [Sunday]. It shall remain consecrated, sanctified.' And thus the pagan Sunday, dedicated to Balder, became the Christian Sunday, sacred to Jesus"--William L. Gildea, "Paschale Gaudium," in The Catholic World, 58, March, 1894, p. 809 [A Roman Catholic weekly].
"in order to recommend the new religion to the heathen:" "The use of temples, and these dedicated to particular saints, and ornamented on occasions with branches of trees; incense, lamps, and candles; holy water; asylums [hermitages, monasteries and convents]; [pagan] holy-days, processions, sacerdotal vestments, the tonsure, the ring in marriage, turning to the East, images, . . . and the Kyrie Eleison."--J. H. Newman, An Essay on the Development of Christian Doctrine, 1920 edition, p.373 [Roman Catholic].
"The mighty Catholic Church was little more then the Roman Empire baptized."-- A. C, Flick, The Rise of the Mediaeval Church, 1909 edition, p. 148. From ancient Babylon came the cult of the virgin mother-goddess, who was worshiped as the highest of gods--see S. H. Langdon, Semitic Mythology, 1931 edition. This worship was taken over as Mary-worship by Rome. Heathen sun-worship on Sunday was likewise adopted by the Roman apostasy.
"In order to attach to Christianity great attraction in the eyes of the nobility, the priests adopted the outer garments and adornments which were used in pagan cults." -Life of Constantine, Eusabius, cited in Altai-Nimalaya, p. 94
"The Church did everything it couldto stamp out such 'pagan' rites, but had to capitualet and allow the rites to continue with only the name of the local diety changed to some Christian saint's name." -Religious Tradition and Myth. Dr. Edwin Goodenough, Professor of Religion, Harvard University. p. 56, 57
"From the foregoing, which treats merely of the more important solar festivals, it is clear that these products of paganism are as much in force at present ... as they ever were, and that Christianity countenances, and in many cases has actually adopted and practiced, pagan rites whose heathen significance is merely lost sight of because attention is not called tot the source whence these rites have sprung. So heavy was this infiltration that Sir Samuel Dill exclaims: "Christianity is only a sect of the Mithraists." -Roman Society from Nero to Marcus Aurelius, p. VII
"We know that Mithraism was a state religion of Rome at the time that the Christian church was established there. Evidently tenants of Mithraism such as Sunday worship and eating the wafer in the mass were adopted into Christianity at that time" -Jim Arrabito "666 & the Mark"
In Stanley's History, page 40: "The popes filled the place of the vacant emperors at Rome, inheriting
their power, their prestige, and their titles from PAGANISM."
"In short, sun worship, symbolically speaking, lies at the very heart of the great festivals which the Christian Church celebrates today, and these relics of heathen religion have, through the medium of their sacred rites, curiously enough blended with practices and beliefs utterly antagonistic to the spirit which prompted them." -Sun Lore of All Ages, Olcott, p. 248
"Yet the cross itself is the oldest of phallic emblems, and the lozenge-shaped windows of cathedrals are proof that the yonic symbols have survived the destructions of the pagan Mysteries. The very structure of the church itself is permeated with (sexual symbolism) phallicism. Remove from the Christian Church all emblems of Priapic origin and nothing is left..." -The secret teaching of all ages by Manley P. Hall
"When the zealots of the primitave Christian Church sought to Christianize paganism, the pagan initiates retorted with a powerful effort to paganize Christianity. The Christians failed but the pagans succeeded. With the decline of paganism the initiated pagan hierophants transferred their base of operations to the new vehicle of primitive Christianity, adopting the symbols of the new cult to conceal those eternal verities which are ever the priceless possession of the wise." -The secret teachings of all ages, Manley P. Hall p. CLXXXV
"...The world, cloaked with a form of righteousness, walked into the church. Now the work of corruption rapidly progressed. Paganism, while appearing to be vanquished, became the conqueror. Her spirit controlled the church. Her doctrines, ceremonies, and superstitions were incorporated into the faith and worship of the professed followers of Christ." -The Great Controversy, p. 50
"The belief in miracle-working objects, talismans, amulets, and formulas was dear to Christianity, and they were received from pagan antiquity . . . The vestments of the clergy and the papal title of 'pontifex maximus' were legacies from pagan Rome. The [Catholic] Church found that rural converts still revered certain springs, wells, trees, and stones; she thought it wiser to bless these to Christian use then to break too sharply the customs of sentiment . . . Pagan festivals dear to the people, reappeared as Christian feasts, and pagan rites were transformed into Christian liturgy . . . The Christian calendar of saints replaced the Roman 'fasti' [gods]; ancient divinities dear to the people were allowed to revive under the names of 'Christian saints' . . . Gradually the tenderest features of Astarte, Cybele, Artemis, Diana, and Isis were gathered together in the worship of Mary"--Wil Durant, The Age of Faith, 1950, pp. 745-746.
Langdon tells us that Mary worship came from ancient Babylon where the virgin mother-goddess was worshiped under the name "Ishtar." Elsewhere in the Near East, the mother-goddess was called "Astarte, Ashtoreth, Persephone, Artemis, [Diana] of Ephesus, Venus, and Isis." This goddess, considered to be greater than any god, was called by these heathen the "virgin mother, merciful mother, Queen of Heaven, and my lady" [which is what "Madonna" means in Italian]. Langdon says she was often sculptured in mother-and-infant images, or as a "mater dolorom" [sorrowful mother] interceding for men with a wrathful god. And thus ancient paganism was brought into the churches and lives of Christians.--see S.H. Langdon, Semitic Mythology, 1931 edition, pp. 12-34, 108-111, 341-344. Laing mentions several other corruptions by which the mother-goddess was worshiped by heathens, that Rome adopted into Christianity: holy water, votive offerings, elevation of sacred objects [lifting of the host], the priest's bells, the decking of images, processions, festivals, prayers for the dead, the worship of relics and the statues of saints.--see Gordon J. Laing, Survivals of Roman Religion, 1931 edition, pp. 92-95, 123-131,238-241.