I mean i know it came with Israelite Slaves to Rome
Nah, it wasn't Israelite slaves, it spread across the Empire via the way of Greek and Egyptian cultists / converts. Once the Greeks were onto something, it was going to spread fast, and far. (BTW they love this "we we slaves" thing, but read the old-testament description of Joseph's time in Egypt - Jews ended up with all the control of the government, food supply, money, land, livestock, and herded (concentrated) the Egyptians into the cities like cattle whilst giving their kinfolk free food and the best land. These are all known modern tactics of invaders disenfranchising a foreign populace - this isn't anti-Jewish propaganda, the bible gloats about it. Then, they get all surprised when the natives rise up against them ... and suddenly
they're the victims. The Jews were just as much bigots as every other race).
Also "Israelite" is really a misnomer, as the historical Kingdom of Israel only existed from about ~900BC to ~700BC. It's seriously over-blown. You might as well refer to Iranians as Babylonians and Sumerians for all the sense it makes.
Christianity was first declared a heretical sect by the orthodox Jewish religious authorities, and thus split off as a separate thing, plus they actively converted non-Jews to the sect, something Judaism did not do. Some people also think that the "one god in heaven" idea appealed to Roman citizens because it paralleled the "One Emperor in Rome", whereas previously the fractious nature of politics promoted belief in a diversity of Gods. plus Christianity scavenged the most appealing elements of both Pagan (Greek and Egyptian mainly) and Hebrew religions.