If he was really nice, he would have offered to protect her without deliberately pressuring and manipulating her into marriage. She made that request as a desperate, last ditch effort not knowing who he really was. He could have easily resolved the situation as a friend. He cares more about getting what he wants than sparing her fear, stress, and trauma.
He never actually tried to pursue her and get out of the friend zone. He just took advantage of a dangerous situation and maneuvered it until it was almost logistically impossible and emotionally fraught for her to refuse.
Even after she was safe (though imprisoned by him) he was still planning the wedding for two weeks despite not even having proposed. He never cared about her opinion, and he never felt guilty about the lies and manipulation
This is so much better than I thought, the ML is really really nice (I mean to the fl) and the FL can actually protect herself!!