I mean, think about it. My grandmother was a piece of shit, which caused my mother to be a piece of shit.

So this probably also happen in affluent families. One of those families is gonna be the ruling dynasty. So in the beginning somebody send an army to conquer lands. Then was really strict (aka: abusive) towards his children in order to find the “perfect” hier to the kingdom/empire. Because of the abuse, the heir grows up to be a tyrant. This chain reaction lasted for centuries, which is why our world is just tyranny after tyranny.

Obviously this is not to say it absolves the tyrants of their wrongdoings, but its the explanation.