Actually it's more realistic than you might think, sudden changes of heart happen all the time he didn't love her because he didn't know her so obviously he wasn't going to act all lovey-dovey towards someone he doesn't view as his lover they didn't make contact much at all so obviously a relationship did not form. he didn't know her he didn't love her she was a stranger in his house would you bend over backwards and mourn the death of a stranger? No. so why villainize him for reacting the same way most people would act in response to the death of someone they didn't know?
I'm not saying that he was morally correct and not even trying to build a relationship with his wife but to be fair he never wanted her as his wife, it was a choice that was made by his parents
I second this
And those few pages of her diary revealed A LOT about her and her mental health that he didn’t know
I already dislike the premise of this manhwa so much. No matter what the Emperor does in this new life for the Empress, it doesn't change the fact he was a shitty person. The Emperor neglected the Empress, even to the point where he was unfazed as he watched her die in front of him. It's completely unrealistic for a character to suddenly change - but lo and behold, he does so after reading a few pages of her diary and suddenly coming to an epiphany that he royally fucked up? Especially to the point where he impulsively decides to turn back time?? for her sake?? pls I don't like this redemption arc that's going to follow at all.