I think you're confusing how systems of government work. For a good description of dynamics in dictatorships, I'd recommend Bruce Bueno de Mesquita, a political scientist at NYU.

To oversimplify, in a dictatorship, the dictator serves at the pleasure of the branches of the army, secret service, and police. If a majority believe he's unfit, he's out. Commanders have a lot of autonomy to refuse orders. That kind of infighting is common in China too. It's nearly impossible in a democracy.