I don't really understand how the king situation works and I've been trying to make sense of it
Cersei was queen
Daenerys conquered/burned down Kings Landing. She has already claimed she is rightful queen of Westeros
Daenerys is killed by Jon, who is both heir of Aerys and the rightful claimant to the throne instead of Daenerys, and her second-in-command/lover so would be the rightful king as he is technically both heir and conqueror
Tyrion and Jon are imprisoned but Grey Worm (who is the current leader?) listens to traitor Tyrion for some reason. After 8 seasons of bickering turns out no-one wants the throne - so lets all vote for a King, cause that's how monarchy works, and let's all choose the guy who can't have kids and isn't even from the realm as his kingdom decides to be independent, even though this makes him the rightful King of the North. Bran then banishes rightful heir Jon to the Night's Watch which no longer exists and isn't under his rule as the Wall isn't part of the Six Kingdoms.
Everyone wanted their own kingdom before, now everyone is happy to be under this one guy they've never heard of? Everybody except his own sister of course. Did they elect a king just to punish Jon so Grey Worm would piss off?