lore explanation:

obviously, before sans took the role, there were many more rulers previously. and the monsterkind's leadership, while officially more so a monarchy, could as well be a dynasty if the two in some way were related, as at one it began being mostly ran by two famillies, the dreemurrs, obviously, and 'the fonts' as sans' family is unoficially called.

anyway, you know what uty is, and you know that in the vengeance route clover's motivation is just them thinking they're delivering some kind of 'justice'.

fuck the fact a storyshift yellow doesn't doesn't really exist, something like that happened in this au.

either way, once sans, who was next in order for ruler, heard about another human coming into the underground from his brother, knowing how much stronger humans are, got the brightass idea of using them to, in some way, assist himself in killing the current ruler, as he was done waiting for his turn.

and it's an underfell au. it wouldn't be too hard to make a soul of JUSTICE believe that killing off the vile monsters is some way of delivering justice. so he did just that, making himself out as a good guy, while beefing up the kid for them to easily wipe out the king of then.

and obviously, word of something like that does get around quickly. so just because he could, why wouldn't he use clover for even more benefit?

this art is him loading in non lethal rounds in his gun, to knock out the kid, to later execute them in front of an audience, to just start off his rule with a bang. and do it he did. and because of how good he made it, by people's choice he always carries out the executions, but that's just some trivia