...........the Roman Empire had not adopted it ? They were far from being in the majority at the time,although growth had taken place over a large area, but within that area they were still a minority religion, often an underground one.
So hypothetically, would it just have withered and died, have torn itself to shreds with all the schisms and sects ?
I think that without the power of Rome it would have done just that, perhaps the Coptic church may have survived until the 21st Century and perhaps the eastern Churches, but the Western ? I doubt it, and we would have ben saved from about 2000 sects, and all been happy tree-hugging Druids !