1. Internal fight for power
2. Constant attacks
3. Decline in gold and silver resources
Explanation:
The Roman Empire is one of the most famous empire from the antiquity and right so, being an empire that dominated much of Europe and at one point all of the Mediterranean coastline. The empire was built gradually on military power, wise policies, and wealth. This didn't last forever though and eventually the empire crumbled.
The internal fight for power was one major reason. The local powerful houses wanted to become even more wealthy and more powerful. They created their own military forces and disobeyed the central power.
The constant attacks were the major cause of the military weakening of the Roman Empire. Constant attacks from the Huns, Goths, Vandals and others resulted in gradual weakening of the army and loss of territory, eventually becoming to weak to defend the empire.
The wealth in the empire was declining too. The resources of silver and gold run dry, and having no technology to be able to easily discovered new ones the empire started to suffer economically, which of course made huge problems with poverty.