He loves his daughter dearly. He is threatened by that bastard king. He once disobeyed him and he killed his wife. It scared the shit out of him if he were to lose another precious being aka his daughter. She is his weakness. In the first timeline, he didn't plan to kill his daughter. He actually wanted ML to save his daughter but she didn't know that so she committed suicide. He didn't want to deepen their relationship so much because the king might be on to something. ML will be the same when he falls for FL, he will eventually understand why he needs to usurp the throne and kill his bastard father