Of the major branches, only those derived from Catholic/Orthodox sects (including Protestants) are those which evolved inside the Empire.
Those derived from the Nestorian and Oriental Orthodox Churches evolved in the Caucasus and Mesopotamia, in regions outside of Rome’s control or where its control was marginal, and in Ethiopia.
But numerous non-Roman branches of Christianity survived?
Christians used Rome as a tool against their enemies much more than the reverse.
I don’t know, I always assumed the later branches evolved from the ones that survived inside empire the first 200 years. I could be wrong ?
Edit phrase
Of the major branches, only those derived from Catholic/Orthodox sects (including Protestants) are those which evolved inside the Empire.
Those derived from the Nestorian and Oriental Orthodox Churches evolved in the Caucasus and Mesopotamia, in regions outside of Rome’s control or where its control was marginal, and in Ethiopia.