Hmmmm....I think you're way off.
The date that the Roman Empire fell is usually cited as 476 C.E. - roughly 400 years after Paul lived. More inclusive historians claim that the decline of the Roman Empire began about 150-160 C.E. and took roughly 300 years. Even 150 C.E. was well after Paul's death.
http://en.wikipedia.org/wiki/Fall_of_the_roman_empire
In ancient times, it was common for rulers to help prevent uprisings by enforcing particular religions on their populace. This is the "state religion". In large empires like the Roman, there could be many state-approved religions. The danger in an unapproved religion is that the leaders might not teach conformity to their followers, and so those followers might become a source of civil unrest - a very, very *persistent* source of civil unrest.
Christians were believed to be an "upstart" sect of Judaism - one that refused to conform to the dictates handed down by the leaders of Judaism and, therefore, potentially dangerous to the stability of the empire. More: it seems either that Christians really *did* start the conflagration that burned Rome, *or* that Nero started that conflagration for his own purposes and needed a scapegoat - and the new, quickly-spreading sect called Christians were handy.
http://en.wikipedia.org/wiki/Persecution_of_early_Christians_by_the_Romans
It should be noted that Constantine ruthlessly suppressed the sects of Christianity in the Empire that did not accept the authority of the council of Nicea. In other words, military suppression of "radical" religious sects - simply because they are radical and *potentially* dangerous, not because they are actually plotting civil unrest - is a common theme in history.
Jim, http://www.bible-reviews.com/