@sukaley Mmm, I could be wrong, especially because my only referent is the series and I saw it a long time ago, but if I remember correctly, the current situation in the Empire isn't good. Both the Emperor and her sister were bad, the Emperor was the worst one since he had some kind of issue with his head and was sick for sex or something. That made him break many rules, abuse of his power, and his people, and he basically affected the whole country and its families to the core. He was kinda "abused" and played as well but I don't feel any pity for him because he's trash and he deserves his end, lol.
As for his sister, she was in a similar position but less bad, there were people who hated her because of her blood relationship with the Emperor, others because she was doing immoral things as him, for example, abusing men and using them as toys for her fun, but also because she abused her power and the power structure of the Palace (this is specially related with her brother), etc.
The motivations are different according to every character, most of the mentioned ones before are relevant in the story. Some were against her because she used them to please her, others were humiliated and 'tortured' by her, idk how far she went with them but I do know that some of them were hurt in their souls because of her, so basically the hatred is deep. The most sensible ones hated her because she used them as toys, she had no respect for them and she also forced them to perform, play music, write poems, etc. for her, just to pass time (that's another really important aspect because she did that to people who hold their honor as the most important thing and those activities were part of their hearts). Oh yeah, she also was reluctant to free some of these men and was an improper woman trying to force them, so imagine her disrespecting them, abusing them, locking them, and destroying their pride. It got worse because some of them lost their families and other things, but I do also remember there were some of them who I didn't understand, Anyway, everything was disadvantageous for her because u can say she was a very improper woman in the past so yeah (idk how to say it, lol).