Acts 24:5-- a single religion Jesus started--The rest claiming to be Christian are in reality a part of this-2Thess 2:3--the great apostasy. They became a house divided-they will not stand-Mark 3:24-26
Not buying it.
Paul was roaming the Roman world trying to keep his churches in line because others were traveling with different theologies. The main conflict being, did one have convert to Judaism before becoming a Christian. Some said yes and that was the Jerusalem faction. Others, like Paul, believed you didn't and circumcision was unnecessary. Paul's faction won by default when the Romans burned Jerusalem. If Paul had lost, Christianity today would be a tiny sect in a minor religion. Paul opened up the possibility of mass conversions of gentiles.
Pagan Rome was as much responsible for Christianity as anyone or anything.