They’d been too close to the cluelessness of the Roman system far too long.
So that’s why the Assyrian Church of the East is so close the Catholic Church despite the fact they were outside the Roman Empire. They broke with Rome and Byzantium in 431 A.D.
http://assyrianchurch.org.au/about-us/the-sacraments
It was under the rule of the Persian Empire and never under Roman rule, either secular or relgiously.
I love your mythical understanding of Catholicism.