I believe early Christians were making Jesus the new God. He was exalted and became the alpha and omega. Many Gods in other pantheons were lesser gods then promoted to top spot. Other gods once they assumed the top spot also took on the attributes of the gods they replaced. Horus got RAs power when his mother tricked RA. Marduk just took the power and absorbed the other gods so to speak. Zeus was another good example.
In the Canaanite pantheon El was the top God but Baal took over. Thier is ample evidence that Jesus was a mix of Serapis, Baal, Zeus , Horus and others. I think this was done as a way of attracting the masses of pagans in the empire to one God.
We can also see evidence of this in the Jewish God. He takes on the attributes and writings about him were also taken from writings about other gods. Marduk , Ashur, RA etc. in fact the Bulla that was discovered and shown to the world last year, Hezekias bulla had a symbol of RA on it. RA was the top God of the Egyptians and Hezekia was an ally of Egypt. So this evidence proves that the Jews were not monotheistic and the top God they worship wasn't always jehovah.