What are the two main reasons the roman empire, the han dynasty, and the gupta empire fell

All three empires experienced problems with taxes. rome had tax revolts. upper class and church were exempted from taxes. han china's officals were also exempted from texes. it was difficult to collect taxes from peasants because they were poor. the gupta did not have enough money for military defense so they taxed. in rome 25 to 26 emperors died within a 50 year span. they had no one ruler to keep rome structured long enough. han china's officals were corrupt.all three empires experienced land divisions which weakened it. western rome was divded from the other half, the west was the weak part. the gupta empire had land divisions were increased power of officals but was bad for the peasants. china was unable to control their large estates. the three empires also experienced invasions which also led to there collapse. rome also fell due to invasion of goths and huns. gupta fell to invasions of the white huns and han china also fell due to invasions with xiognu nomads.