Did you really think it would be that easy

The king is a puppet of a dictatorial deity. The solution is to overthrow god.

JRPG style
I tried that. The paladin Divine Smite'd me :(
- Secular Smite them back, easy.
Reach heaven through violence
The king is a puppet of a dictatorial clergy, the solution is to burn the church down with the clergy and monarchy inside.

It seems like any sufficiently rich person, like a monarch, could essentially have someone on staff - maybe multiple people - whose entire job is to periodically cast True Resurrection, naming the rich individual. If they aren't dead, the spell fails; if they are, they come back to life, and can name their assassin.

Assuming D&D 5e rules, this is easily countered by casting Gentle Repose on the corpse every 10 days, or any other method of preventing natural decay.
True Resurrection can only create a new body if the original no longer exists.
- I guess this comes down to DM fiat as for what constitutes "touching" the creature. For example, what if the person casting the spell had a hair sample, or a severed finger or some other item from the monarch's body, which they were also taking any of those steps to prevent decay of?
  The 3rd Edition version of the spell is even more ambiguous. RAW, it doesn't prevent you from "unambiguously identifying" the creature through a means other than touching the body even if the body still exists.
- Or stuff it in a bag of holding!
Or they could just have some Clones.

"~~Nanomachines~~ Invulnerability, son."

Weird timing.

Is it? Why? :o
- I think they are referring to the No Kings protest going on in the US right now.
  https://www.nytimes.com/2025/10/18/us/politics/no-kings-protests-trump.html

NANOBLESSINGS, SON!

This really gets into the foundational expectations of the setting.

In a reality structured to allow for Heroes, a leader must be one, or else be replaced by the next one to stroll through.

Hero might be the wrong word except in the traditional sense of demigod. There's an implicit positive moral judgement in the term that being a monarch has very little to do with.
I'd also argue that it's more that monarchy by its own self justification is based on the idea that the king protects, and therefore effectively owns, his subjects. A king might do that by effective governance however. If they can't do it personally they'd need the loyalty of a champion, for example.

Nobody would rule by birthright in a D&D world. Any leader of a country would have access to Clone, and would have no need for inheritance.

Funny thing, there was a 2e setting called Birthright, which pretty much made the game about developing land as a lord, rather than dungeon delving
- Oh. I just learned about this. I have no involvement in this channel but this video was neat. https://www.youtube.com/watch?v=WsGk9M-4dq4

Lord British be like