By 300 AD Mithraism and Christianity were both popular - Mithraism had at least a 900 year lead at that point - but Mithraism lost, and most of it's rituals were absorbed by Christianity, in order to make Christianity more palatable to pagans. Christmas rituals are warmed-over pagan rituals. Yule log is a druid ritual. Decorating trees, a druid ritual. Easter egg - pagan ritual. Bunny, pagan fertility symbol.
Jesus? Nope. Dionysus!
The resurrection myth goes back to the Sumerian creation epic, Enuma Elish. Osiris followers found salvation in death and his rebirth. 1,400 years earlier.
Krishna was born from a Virgin.
Frigga was impregnated by Odin and bore Balder, a healer who was to save mankind.
Baptism in water was already a common pagan ritual.
Mithras followers found salvation in the blood of a Bull.
Look, I know you can go and find some kind of churchy website that proposes to refute that Christianity and Mithraism or other pagan rites have anything in common, but you can also find web pages that say that Muhammad is really the last prophet, and other web pages that say they were both space aliens, if you look hard enough. There is quite a bit of scholarly research on this topic published outside the realm of "biblical archaeology," a phony science which starts with an unquestionable assumption based purely on faith and then selectively picks facts to support it.
My point here isn't to upset you. I'm not "anti-Christian" as I appreciate some (not all!) of the roles Christianity has played through the last two millenia. I don't care if you believe that either Jesus or Kermit the Frog is your messiah. It's your belief to have. My point is that Christianity is technically Judaized paganism which predates Christianity. It's rituals and stories are far from unique. Asserting that Christianity as practiced today has Judaic roots is only telling part of the story, asserting that it has PURELY Judaic roots is a flat out lie.