As I have often written here and in other forums and said from time to time (with apologies to Santayana): Those who cannot remember Church history are condemned to make it up.
And they do!
There are a plethora of tantalizing clues that are open to many interesting interpretations. To think that early Christianity was unaffected by the practices and even the beliefs of ... o say ...Mithraism, the Isis Cult, Roman gods and goddesses, Greek myths, Judaism, etc. would just be plain stupid.
After all, Pope Benedict shares a title ... Pontifex Maximus ... with Julius Caesar who once held the job. None of this denigrates Christianity or weakens it. Protestants in the Calvinist line would love to believe that their sects are untainted by the Romans or Greeks, even while reading St. Augustine. Good luck with that!
Once St. Paul decided that one need not become Jewish before becoming Christian and decided to "market" Christianity to the Hellenistic and then the Roman World, who can say with certainty exactly how wildly differing groups of converts actually practiced the faith or what actually went on with their prayers and ceremonies in their churches? It was a good while ago!
After Constantine made Christianity the state religion of Rome, things may be a bit clearer because of somewhat improved record-keeping, or at least more consistent record-fudging. Though one always wonders just how many "pagan" priests just converted ... themselves and their temples to the new official faith. In like fashion, many a Roman Catholic priest became an "Anglican," ... and now vice-versa!