This is just a silly series with no intended depth, but I still think it's a good choice the author has kept Krum as a demon lord. She didn't turn good or anything like that. Her priorities merely are extremely weird compared to the other demon lords, due to how her revival happened to happen. She's not trying to save the races, she's trying to save her source of delicious food. Of course, since this is a silly series, she ends up being pretty friendly, all in all, but that can't be helped as it wouldn't really work in this kind of story otherwise.