It's the nature of things. One word: evolution! Let's imagine a society where power grabs are checked. Then we have an unstable equilibrium. Lucky and shrewd p

It's the nature of things. One word: evolution! Let's imagine a society where power grabs are checked. Then we have an unstable equilibrium. Lucky and shrewd persons can become able to evade the checks. It's a bit like immunity of bugs to poisons. Bugs that die off don't reproduce so the system is self-selecting to immune bugs. It's a pity.