Answer: Cause: A king/emperor is corrupt by taking taxes to himself. Effect: The army costs don't get paid, roadwork doesn't get paid, other stuff that taxes give doesn't get paid to which causes the place to fall.
Explanation: This actually happened in the western Rome empire. The emperors took taxes to themselves and armies don't become strong and roads don't get built. This is why the western Rome empire fell but the east side kept going.