Name one where the dictator and his cronies were not also embezzling the wealth of the country and living it up with their rich buddies. That's what they grab power for.

Even if the guy at the top has ideological principles that forbid such behaviour (rare) and isn't a hypocrite about them (super rare), there is always someone high up in the hierarchy who is in the market for favours, and due to the nature of a dictatorial hierarchy, essentially untouchable.