You never explained how power imbalances affect human survival as a species, which is key to your original evolution argument. Revolutions and instability represent periods of unhappiness, just as brutal authoritarian systems do, but neither is much of a threat to survival of the species or evolutionary fitness in general.

Nuclear weapons do represent a real threat to species survival but still the only country to have used nuclear weapons in war is a democracy, so the jury’s still out on that.