Well, yes, he had committed himself to a great extent with Anne. Had he backed out of it he would have made himself look foolish, and he really had too much to lose not to continue with it. He needed an heir, and believed she could provide a healthy male heir. There was no reason to not to believe that. As it was, she produced a healthy female who wasn't exactly an heir. But he didn't know that. I suppose he already thought enough reputations were ruined, so why not marry Anne Bolyen?