The Roman empire fell for many reasons, and Christianity was a factor. The largest factor though was they became completely dependent on outside forces to fight for them as people who resided in Rome were considered too elite to fight and had become too lazy and entitled to keep their people in check. These people realised that the ruling elite wasn't helping them, and they were better off without them. They couldn't even muster a force when attacked. They had become corrupted significantly. Christianity was an issue as the doctrines differred throughout their empire which caused fighting between their people. Also the morals of "Rome" differed from the teachings of the church and other parts of the empire saw Rome as a debauched part of the world. The Eastern empire didn't last much longer either as Justinian effectively destroyed that part of the empire by being aggressive and not understanding he wasn't as strong as he thought. Lessons for all of us
