And so I learnt that paganism crept into the church during the reign of Constantine of Rome when he besought a monotheistic religion to consolidate his reign as emperor of Rome.
By this time the Christian were persecuted and vilified against the polytheistic view that prevailed in Grecian and Roman Empire.
and so in 313BC he upheld Christianity as religion of the empire as well as that of the state and Rome.
This was to serve dual purpose, firstly to bring the people together under one religion as a way to achieve power and authority, secondly as a means of consolidating a similar hierarchy in Roman Empire.
The Christians once vilified, persecuted, considered heretic and burnt at stake now suddenly is embraced and made the state religion with the Church head considered so powerful he can make no wrong.
However due to the need to accommodate pagan worshippers under the religion of the state, the Emperor introduced over a period of time in cohort with the Church, adulteration of pagan worship which is still held and practiced today.

The Pagan worship introduced into the Church are chronicled below:

300 BC Adoption of prayer for the dead from Hellas.
320BC Adopted wax candles for worship from Pagans.
321BC Abolished the Sabbath, adopted Sunday Service worship after the pagan who worshipped the Sun God, Mithras.
325BC Abolished the Feast of Passover
354BC Introduced Christmas as the Birthday of Christ after the birth day of the Sun God, Mithras
375BC Began the worship/veneration of the dead, especially the Saints
431BC Began the worship of Mary from the goddess of the heaven Ashtoreth from Pagans: Introduced the term "mother of God"
in reference to Mary.
493BC Defeated Herules which opposed the catholic Church
496BC Converted Cloris, King of the Franks, who held the political and Religion Powers in Rome.
534BC Defeated Vandals which opposed the catholic Church agonistic view.
538BC Defeated the Ostrogoths who opposed the Roman Catholic church.
600BC Introduced the Prayer to Mary, dead saints and Angels into Christianity.
709BC Legislate for kissing the Pope's foot.
754BC Established the Vatican as a state
890BC Commenced the worship of Joseph as the Father of Jesus.

The Tiara worn by the Pope signifies he is God in the heaven, earth and Hell, and the official title of the Pope is in Latin is Vicarius Filii Dei (Vicar Son of God). If you add that up using Roman numerals, you get 666.

Again ...what do you know?
Hitler was a strong Catholic, he believed killing the Jews was fulfilling God divine judgment for a set of people who had killed Christ and that they deserve death, his position was blessed by the Papacy who even blessed mass before he started the holocaust.