(repost, added more details)

Anyone else headcanon the SOULs coming back into the previous humans' bodies after the True Pacifist route? Cause they technically didn't die as their souls are still in tact. As far as we know, they could've simply gave up their souls. Or maybe giving up your soul kills you anyways. But I like to imagine the humans are in a state where they're not alive nor dead, they're just waiting for a new owner, a new soul to fill the void in their bodies. Maybe a fanwork could explore that. What happens when you steal a soul when you don't have one? Lots of possibilities..

Then, there's Kris. Kris rips their soul out multiple times throughout Deltarune and is able to move around freely and regain control, if just for a few minutes. Who's to say other humans can't do that either? Asgore would actually need to kill the humans AND their soul in order to actually wipe them out, but he didn't. They're just in soul capsules.

Of course, I could just be dumb and none of this really matters and that they just die anyways, but it's just food for thought