
To be fair, no one would like someone who obsesses over them, follows them around, and invades their personal space. Anyone would be thoroughly creeped out by that kind of behavior. He only started liking her when she started respecting him and his boundaries. She herself admits that she was selfish and foolish in her past life. Who wouldn't like someone who was intelligent, respectful, dignified and beautiful to top it all off. Other people only valued her for her looks, while he cared about what was on the inside.

It's possible to change your opinion of a person as they change. There are plenty of people that I've disliked at first but as they grow and improve as a person, I start enjoying the time I spend with them. His change in feelings towards her aren't all that unreasonable. Plus, she's second in line for the throne. The only princess of that kingdom. He can't really avoid her when she approaches him, and he's bound to notice a drastic change in her demeanor. And she is very charming so...
Tbh I’m seem like that person but the fact that he is only liking her now because of a personality and full demeanor change is kinda like almost every other story idk man like what did he want from her…