This is one of those movies where the villain is fueled by fevered dreams of revenge against the good guy and will stop at nothing, even if it is undignified and desperate. Everyone knows he is going to die, but he doesn't care as long as he at least takes the good guy with him...Gladiator is a good example.
Anyway...I think its possible that Webber is haunted by Self to such an extreme that he is willing to ruin himself and everyone near him just to get one last desperate shot at him. But we all know how this movie ends. #TSC