So how did it really happen, and who was in charge of Rome when the Roman Empire finally collapsed?

I'll give you three guesses. All of them begin with 'C'.

Flavius Valerius Aurelius Constantinus came to power as Emperor Constantine in AD 306, and in 312 he converted to Christianity, becoming the first Christian Roman Emperor. Prior to that Christians had been persecuted and many of them martyred, but the religion was now tolerated in the Empire.

Constantine's conversion to Christianity is often attributed to a dream, which influenced him to march into battle with Christian symbols painted on his soldiers' shields. He won the battle, attributed it to divine intervention, and the rest is history. Without that dream he would probably have won the battle anyway, perhaps not become a Christian at all, and the whole course of religious history might have been different. 'Might have', however, is never written in the history books.

Despite this 'tolerance' of Christians, it was only in 391, during the rule of Theodosius I, that Christianity became the official religion of the Roman Empire. By 476 the Empire had fractured into two parts and the last emperor of the western Roman Empire, Romulus Augustulus, was deposed. The eastern Roman Empire, which later came to be known as the Byzantine Empire, continued for a further 1000 years, but what we know as 'The Roman Empire' ended in 476.

Christianity was in power when Rome fell. And it only took 85 years for Christian rule to wreck a civilisation which had been founded in 753 BC, some 1200 years earlier. Let it never be said that Rome fell because it was an evil, cruel empire, ruled by pagans who persecuted the Christians. In fact, when it stopped condemning Christians, and was in fact ruled by them, it all fell apart.

Before Christianity, Rome tolerated any and all gods, and allowed their followers to worship as they pleased (except for some really weird, sicko cults which were banned). You could worship your gods so long as you recognised everyone else's gods. The rule of thumb: be tolerant of all other belief systems.

Of course Christians didn't like that. With their one god they refused to accept the worship of other gods. They refused to tolerate other gods. They wanted everyone to worship their god and abandon all the others. Sound familiar? Wonder why they were persecuted? Because they themselves refused to tolerate other religions.

This is not the whole story, of course. The fact that tribes such as the Goths, Visigoths, Vandals, and, most famously, the Huns (under Attila the Hun) weakened the fabric of the Empire, was key to its eventual end. But Christianity was in power when all this happened. Christian rulers could do nothing to stop it. The Christian God did not save the Roman Empire.

And then, of course, 200 years later, came the Muslims, who ended up slaughtering half of Europe and eventually putting an end to the eastern (Byzantine) Empire too. But that's another story!