Two problems that led to romes decline

The two MAIN reasons that Rome fell was:

Rome was an Empire,meaning it had a vast amount of land as "Roman", as Rome could not provide security to their people, they were open to attacks from their enemies.

The second reason, is that, Rome, was corrupt. You had politicians who were self-centered, they didn't care for anyone or anything, who only cared about themselves. This made Rome weak, there were traitors everywhere in the Senate.

So, you have a weak government system, and once foreigners started attacking Rome, well, the Empire fell.