Because what he did was obviously love, at first he was still supporting Empress but seeing the person he loves between other men, plus not even smiling to him whole heartedly made him go crazy.. And i find his actions like a child's; trying to make the person he loves jealous, in the end he gets jealous and not even accepting it's a misunderstanding.. But this part of him made everything worse, he wanted yo make everything as his own way. Of course it would end as losing what he had; her, the baby which isn't his blood.. He had to find everything out with losing, because he is a royale he would have everything what he wanted and he thought Navier would stay by his side. I just can't stop thinking by others' povs, he was just a kid who wanted to make her jealous, that's it honestly, he wasn't grown up
well his "childish" actions hurt her severly since they were childhood friends after all, not plain strangers even if it was a political marriage. He lost her simply because he was selfish. Selfish enough to hurt the person he supposedly loved. No that's not love, because just to please his egocentric desires (including getting her attention) he didn't even bat an eye on humiliating and hurting her. You should feel sorry of her instead, she had to endure this sort of treatment just because this fool felt insecure.He wanted to use her to cover his insecurity, not win her love. He treated her like so like i said before, he got shit in return. All actions have consequences, including actions that are done for egotistical reasons. She also got rewarded for her endurance.Just because she wasn't acting like he wanted her to, he went ahead and used cruel means to shape her his way. No sir, when you love someone you use patience and understanding, you even let go if needed.
I know i really do, when i was reading manhwa i hated him so much but after novel i took him a pity, this selfishness comes from he always got whatever he wanted because he was a prince, and this made him blind. That's why i feel like this but it doesn't mean i support what he does, i am not a person who likes to hate and just like i said i wanna see others' povs to feel. I do that since i read villainess/villain manhwas so i can't stop thinking.
Well, many people are childish, even pedophiles and killers but still it doesn't change what they did neither are they deserving of our pity, even if they had a bad childhood or any other factors that made them act like that since in the first place, nothing can make you do anything, if you don't truly want it yourself. I don't agree with you but i respect your opinion. Also, I'm not attacking you or anything, in case i gave you that impression (I've been misunderstood a lot before)

What happen to rashta and her unborn kid ? What happens to the trashhoe king at the end with Rashta?