Those put in positions of High authority have slowly gone morally corrupt

Sans is the mayor/senator of the snowdin replacement, he's very much like Enoch from OFF

Papyrus is simply a gravedigger, he isn't exactly evil but the conditions they all live in have made him hard

You may be asking, "How is Papyrus a grave digger if monsters dust when they die?" Monsters have partially lost touch with magic due to becoming corrupt and have adapted to this by becoming more physically built (as opposed to being mostly magic with little physical mass, it's more like 50/50 now)