> Tyrannical governments seem to be the default because it's the easiest way for the powerful to control the powerless, which is the fundamental purpose of most governments throughout history.
Okay, but that's the whole nature of OP's question: Why does tyranny arise again and again, as if it were a natural equilibrium state of some kind?
I don't see why government should be treated differently from other institutions in analyzing this question. Deebo and Lord Farquad were both tyrants; was the nature of their tyranny any different, just because one happened to represent "government" and the other didn't?
My proposition is that it requires constant effort and vigilance to prevent the rise of tyranny, because the forces that lead to tyranny are ever-present. So any society that exists temporarily in a non-tyrannical state is still subject to power grabs and takeover attempts by would-be tyrants.
Maybe you're implying that the existence of a state or government is what facilitates such tyranny; I've heard that one many times. I contend that if the state did not exist, then other people and institutions would fill the same role; that the nonexistence of a state would not represent an impediment to tyranny; and that the existence of a state is not itself a strong indicator of the presence of tyranny.