Thank you for this. While reading the manga I was also thinking the same thing specially when they showed flashbacks.
I recently read a novel called "After divorce I still wore your jacket" they get divorce after 15 years of relationship ao being so in love but they separated due to love too. I think main fault of this emperor is that he searched for love elsewhere rather than trying it out with empress again. To rekindle their old love. I think being heirless was also affecting him too much. All thing aside he's still a trash (〜 ̄△ ̄)〜

I have read the novel up until Naver remarries. I just want to say that I do not like the Emperor but at the same time I feel conflicted because his love is truly for the Empress aka Naver but it's twisted from misunderstandings.
I believe the Emperor at first liked Trashata because he gained affection from her unlike the Empress who was cold towards him. In the novel they talk about or they think of the past and it seemed they were very much in love yet, as time went by the began to believe that their marriage was truly just political instead of actual love. That is where the misunderstanding began, they both actually liked even loved each other but due to their cold demeanor towards each other over the years they began to lose sight of that love they had for each other.
I'm not sure if I explain myself well but due to their duties and responsibilities they began to act their roles more and instead of showing affection they probably thought the other doesn't love them as they did before and just thought of their marrige in a political way.
I know the story is set in this way that it is, but to just imagine that the Emperor were more loving to the Empress and the same for the Empress towards the Emperor the outcome could be different lol
Also as far as I read in the novel, it seems that Trashata isn't really devious persay, like she isn't power hungry she genuinely just wanted a better life than the one she had. But she does think that "what will happen if the Emperor gets tired or finds someone else to love?" And she doesn't want that because she's afraid to be a slave again and to endure that torture again. So I sympathize for her just in that point of view haha. I just think she becomes twisted because she still a airhead who can be manipulated easily by others, even if she's getting proper education.
In reality this post was to kinda look at the characters in a different light instead of all the negative things people say haha but I wont change your opinions since I still dislike the Emperor and Trashata very much but still see where they are coming from.
Spoiler on the lowkey :p
I feel bad for Prince... well King Heniely (sorry I think I spelt his name wrong) because he truly loves Naver yet Naver may be just developing feelings for him but she truly doesn't see him that way as of yet and just thinks of their marrige in a political way while Heniely believes he is receiving back the same affection he has and will always be giving Naver haha I just find it sad and funny becuase it's a kinda of a cliche yet it gets on nerves because this man truly loves her yet it's as if she can see the love which is right before her eyes
Thank you for reading my Ted Talk ;)