By one guy, with a plot device arrow. Not by the militia.
Because he's a dragon fighting peasants and why should he need to?Why wouldn't it?!? Seriously, why the flip, wouldn't the Dragon hire allies? He knows his own power and vulnerability.
Yes, and Batman spends lots of Batman stories not killing the Joker, despite the fact that doing so is logically and ethically the correct choice.Lots of folks do, which is why not all Superman or Thor stories have them tyrannically running the government, in fact that's the vast minority of such stories.
Yes, when you try to oust the current king without enough force to do it, you fail. Because the king has more force and is therefore more legitimate. Not a hard problem.No I don't. Period. I have a lot of study of history. Simply being able to take over a country, doesn't really do much for you, just look at any failed coups. An adventurer killing a dragon won't make the king look weaker in a way that the adventurer will be able to exploit, but rather in a way that other nobles will. The same as we can see demonstrated historically.