:...Edward Gibbon’s Decline and Fall of the Roman Empire, which advanced the theory that the rise of Christianity was the cause of Rome’s fall.”
I’m no scholar, but I would say the fall of the Roman Empire was likely from the fact that they tried to run the whole known world back then. Many small city-states and impoverished countries to have to support and keep in line. To much to control for one government.
Spread themselves too thin.
I think the fall of Rome had a number of contributing causes, but Christianity wasn’t one of them.