I said they felt he is awful. Maybe he felt they are awful, too. It is a thing that happens in human relationships, that people end up disliking each other. We have only heard one side of the story here.
It is a pretty normal thing that people don't get along with each other, for whatever reason. Just because one party goes public and frames the other as a horrible person, doesn't necessarily mean they really are.
If nobody who is disliked by somebody could become boss, there would only be very few candidates left.