What were some of the main factors that led to the fall of the Roman Empire?
Perhaps the two main and key factors that led to the fall of the Roman Empire would be the disunity of it's people towards the end and lack of great leadership. Though the rise and fall of the Roman Empire (750 B.C. - 476 A.D.) it had many rulers. Of which there were some good and some bad. There were emperors that were known to be great philosophers, writers, poets, as well as great military strategists. Rome did however have its share of bad emperors as well. Some examples being Caligula, Nero, and Commodus. Rome had always had its fair share of bad emperors. But there always followed good emperors to correct their errors. At Rome's end however, there was really no good rulers. For example great generals like Stilicho were killed because the emperor feared losing his throne to them.
If you kill your best generals, your army will never be as good as it could be.
Another important factor is that of Roman unity. The early Romans who built the empire stood united. However at the end the Empire had two capitals, Rome and Constantinople, each with its own emperor. In earlier times Rome had been something special, something revered. But the later Romans only sought power for themselves. Almost every general secretly had his eye on the throne and was ready to overthrow the emperor and take power himself. The armies spent a lot of time fighting each other for power in Rome, rather than fighting the enemy. Which eventually led to the fall of the last great empires of the ancient world, as we know today.