Ah, both dudes just want into the panties of the 3rd Heavenly King and she is into him, so he had to go. Simple. Even though "You are the weakest of us." is no reason. After he is gone, somebody else is the weakest of them. In itself being lvl1 and standing with lvl100+ characters means that something frighteningly freakish is up with him. I'd be more worried to encounter such an lvl1 enemy than some lvl100+.
He totally should have shown his power to the demon lord back then. And then yank that corpse form his new throne.