Power and wealth is always asymmetric. The effect is competent people holding power and building some impressive society -> slow reversion to the mean of that society's elites -> a challenge comes up that requires renewal and an above-average response which they can't meet -> collapse.
To me it seems like there is a lot more to this building-flourishing-decay-collapse cycle than power and competence with regression to the mean. I first got interested by this topic after reading "The Fate of Empires" [1] where the author puts the "blame" so to speak, not on competence, but on the generational gap. His thesis is that it takes approximately 10 generations before the values that built the society are no longer followed by their descendants.
