Where did I say players don't get to redraw fantasy maps?
I said that kings and other high leaders are high-level characters, and surround themselves with advisors and bodyguards of similarly high level because it only makes sense in a universe where people can become superhuman with enough adventuring. The players don't just get to shank the king and take over like you implied
I made no implications. I stated directly that they get to do so.
If they want to kill a king they'll have an actual fight in their hands (including the equivalent of a dragon's lair's worth of magical countermeasures in the king's castle) and if they win it good on them. They still have to gain control over the rest of the kingdom, because most national entities aren't ruled by "you keep what you kill".
What makes you think so in the world where two hands explicitly can be stronger than four?
If players want to take over a kingdom, they have to do it either politically by gathering allies within the kingdom before their attempt, or militarily by bringing in allies from outside of it. Once everything is in place, then they get to fight the king. Just pretending a bunch of adventurers can stab a king and claim rightful rulership over anything but a bandit warband is retarded.
Why do you want to play heroic fantasy, of all genres? I'm asking quite seriously. I mean, your scenario belongs in historical fiction or low fantasy that explicitly emulates history, where, of course, a bunch of adventurers still totally can stab (or abduct, or poison, or otherwise eliminate) a king, but they will have to be sneaky and clever about it, and they will need allies and soldiers and supporters and shit to actually benefit from such action.
But fantasy? Let's bring some more examples shall we? From pre-DnD times, and books only, so no really crazy shit here. Oh, all right, there is crazy shit here, just no characters with free nukes on demand.
In
The Broken Sword the main character literally cuts a king to pieces after hewing his way through that king's army, and single-handedly turns a hopeless last stand into a crushing victory.
Elric of Melnibone personally kills a whole bunch of rulers, and slaughters the entire ruling counsil and sorcerer-soldier army of a major city once. He wasn't even using sorcery or dragons that time. Other Moorcock's characters usually have more need of armies and mundane weapons, yet under right circumstances still topple empires and slay gods.
Princes of Amber have no real rivals but each other and a handful other entities comparable in stature, all other creatures are tools and pawns. Much of their activities are centered about overthrowing and killing whomever of them sits on the throne at the moment. (Note, that even some of characters from other Zelazny's books would look on abilities like "can recruit a few hundred thousands of normal humanoid soldiers" or "moderate physical enhancement" and ask why these weaklings are supposed to be a big deal. So would people wielding most versions of DnD magic.)
Fafhrd and Gray Mouser are far towards the low end of fantasy, have comparatively limited ambitions, and live in a somewhat-absurdist world, so rulers tend to drop dead around them without their direct action. When dealing with things like a huge pirate fleet, they need to deploy cunning and plot devices. Yet they still have crossed blades with princes and murderhoboed their way through powerful organizations.
I hope you get the idea. Heroes do heroic deeds. Fantasy heroes do fantastic heroic deeds. Cutting down a king by your own hand may be not even be particularly noteworthy. Like, how slaying of Taur Urgas, a king of a big realm, in
The Belgariad is a fairly minor episode, because that book series deals with battling an evil god, not a mere king.
Now, please tell me, why heroes in DnD, whose abilities and written and intended can greatly overshadow most of the people mentioned above (at least without the latter's plot devices) should find shanking kings to be so inherently difficult? Please do not restate the already-noted argument of the setting somewhat undererstimating what the game allows the characters to do, and being quite liberal with assigning levels (not that this only became really noticeable, when the level scale was compessed to 20, yet NPCs mostly did not went though appropriate downleveling, in fact, often the opposite - in the earlier editions, level 10 bandit leaders were more understandable, as the maximul level ranged from 29 to 36),
The argument that the world must keep itself stable, because it hadn't fell apart yet, is similarly not an argument in the first place. If the interesting times are upon us, the adventure is happening and the heroes are needed, the world is obviously not stable. Like, by definition. In fact, look at actual DnD worlds, and at how often they suffer humongous catastrophes, up to and incluiding alterations to the very laws of reality. Clearly, mere political change should not be a big deal...
...Yet it often is. In my opinion this is just mostly the matter of convenience that turned into a deeply-ingrained habit. The same core reason why nothing ever really changes in capeshit settings, despite parades of aliens, gods, AIs, and whatever the fuck staging one crisis after another. Redrawing the map and thinking through all the cascading consequences is just an extra hassle. This argument I can accept. But I'd prefer if people defused such problems by methods already mentioned in this thread, like making sure that the local ruler is PCs best buddy, and directing their energies towards conquering Dens of Evil. Instead of suddenly pretending that the king and his retinue were always high enough level to handle the Dark Lord from the Den of Evil, but relegated that work to PCs for some reason.
P.S. And all of this is related only tangentially to the reason why bounded accuracy sucks. It does not suck because a horde of guards can eventually overpower Conan. It sucks because a random guard can succeed at climbing Tower of the Elephant or killing a vulture with one's bare teeth, and probability of success won't even be that miniscule.