Answer:
Corruption in the government, social instability and the inability to manage vast borders eventually doomed both empires.
Step-by-step explanation:
Corruption in the government: There were many people inside the Roman empire that had their own interests and that caused many problems that eventually the empire couldn't handle.
Social instability and the inability to manage vast borders eventually doomed both empires: Many people were in really poor conditions in both governments and that problem, along with their problems in the borders, made them collpase entirely.