Totalitarian societies in general are kinda brittle. And part of that seems to be the difficulties of getting the sorts of leaders they had early after they have been in place some time. Growing up in a totalitarian society has its effects on your personality, and even if it didn't, there's the little matter that the skills need to rise and prosper in such a society, so as to be in a position to take supreme power, are not such as to make you an effective dictator. Keeping your head down, toeing the party line, saying nothing so it could not be used against you -- once those are your habits, they will stay your habits. Supreme power doesn't include the ability to throw them out the window.
North Korea seems to be keeping the ball rolling -- but by reinstating a monarchy. Hereditary monarchies do have the problem that you never know what sort of heir you can produce, even if you choose among the monarch's children, but it does let you raise the child in the expectation of power. Though some will suffer from the helpless period before the monarch dies, it is imaginable that you can pull that off.
