Factors that contributed to the decline of the Roman Empire were:
Incompetent rulers placed huge tax burdens on the Roman citizens.
Rome could not grow enough food and maintain a large enough army to fend off barbarian tribes.
Explanation:
Rome was the center of the antiquity for ages as it was the biggest empire in the world but in the end of it it had become too big for proper management from the seat at Rome
By the time it was ending it had been in a continuous struggle against the barbaric tribes up north that had been weakening thee hold of Rome on the area.
It had become too big to sustain itself and the profits from the agriculture of the empire were just not enough.