That's the real question, isn't it?

I was thinking about it. When a ruler becomes unfit to properly lead his people, then it wouldn't be out of the question for a sound replacement to be found. Now clearly it would be difficult for them to kill the current king or even lock him up somewhere, but someone else could always step forward as the "son" of the king, legitimate or otherwise, and that individual could take over leadership on a political level.

You would know more about this than I, of course.