The best way to counter that lack of knowledge would be to encourage education for all, along with popular interest in the welfare of the country. Which is exactly what an unfit king would want to avoid, but well-educated older generations would counter that. ...Unless a country is afflicted with a series of long-lived bad kings, which would be terrifyingly unlucky.

[Or commonplace in certain worlds, perhaps, but Cecil really doesn't want to know about those.]