@keks503 there's something going on with his family and the crown princess, she has made clear her interest in Fei Yue and has checked his purity mark, also his mother is a pawn to her. So, he was considering the divorce for that. Doesn't matter that he truly loves his wife, since it's a scheme of his family it counts as a betrayal in his behalf.
And if I'm not wrong, white haired cutie is the one he feared to become the second consort, the one that the original 3rd princess loved. And looool poor consort xD he was so waiting for this to happen hahaha 😂