
right??? it felt like a sudden redemption arc. hyunjae in the first timeline didn't even bat an eye to mc when he said he was useless but now he realize how he loves him. it was out of nowhere in my opinion, although the build up to hyunjae regretting it & realizing he ruined everything was pretty nice - and regardless of the author making changes in his character, i think one way or another, it was bound to happen. the seegs tape that was set to ruin them came from hyunjae himself after all.

maybe it's because in this life he experienced nokyoung leaving his side and realised how "special" he was? the only worth he saw in nokyoung in the past life was from his attractive looks and once nokyoung's face was permanently obscured he labelled him "useless", but in this life he really saw his acting potential and how much better he became after he left hanool. like he did think "i had no idea you were such a good actor".
TL;DR "i'm just an idiot who didn't know what he had until it was gone..." -- i think he needed to experience this for him to go through character development.

totally agree about the drama, especially that break up lmao
i personally thought he started to care for nokyoung because nokyoung stopped being his obedient puppy in this timeline, he showed that he was a "real person" with real feelings and won't be his doormat any longer, thus leading him to actually see nokyoung in a different light and actually considering him as a human instead of just a plaything to make money with. hyunjae had absolut no respect for nokyoung whatsoever before, and now actually gained a liking and respect by nokyoung stepping up to him (basically the trope a lot of shojou use, be upstanding towards the bully and they will fall for you, lol)
also, since nokyoung isn't doing what he asks him to do it leads to more trouble with that...cousin/brother/whatever dude, making hyunjae realise and hate how much he's used by him and missing nokyoung, who he believes would've never betrayed him if he would've been nicer to him and could've actually been successfull too. he basically wants the loyal nokyoung that kang got and regrets losing him, thus maybe trying to at least do something for him, because he realised how good nokyoung was to him before compared to that cousin dude?
all in all i don't think him being nice is weird considering how different that timeline went in regards not only to nokyoung but also his ?lover?
lol as the story progressed it just kept getting more dramatic. it felt very typical soap opera drama.
anyway, with that being said, i do have one small comment regarding hyunjae. during the original ending, he tossed Nokyoung aside heartlessly, saying he's "useless now." In the new ending, he seemed to actually give a small shit about Nokyoung, maybe even cared a little for his well-being. based on the things revealed in the new ending, he was simply doing what hanil wanted him to do, but he actually would have preferred to not hurt nokyoung.
now, i think this is a big inconsistency compared to the original ending. if all of the things revealed in the new ending is true, then in the original ending, hyunjae should've reacted a little differently. someone he potentially cared a little bit about just got attacked. his reaction was simply too ruthless for someone who may have wanted well for nokyoung. which makes me think hyunjae was definitely meant to be an antagonist until the end but author must've changed their mind about his character development later.