@Hexador
@RubyG8396
As an Asian, I can confirm harem was the norm in the past. My grandfather had 3 wives. However, my grandmother described that was like living hell, she had a miserable life so after my country passed a law that deems polygamy illegal, she personally made sure that none of her sons cheat on their wife.
That aside, in this case, cheating here isn't used in our modern definition. The prince can have other wives, owning harem is not the problem. The problem here is he chose that other wife and cast aside his first wife, who sacrificed so much for him. He demoted her and that is a huge disgrace to a consort and her family. Demoting means that her living conditions like food, clothing, etc. will be decreased. He even placed her on house-arrest and if that continue, she would have to live as a prisoner for the rest of her life without seeing her family, became a living corpse, a life that all consorts loath.
I can't quite grasp what RubyG8396 said though since having a harem was the norm for nobles, kings, princes, etc. I grew up reading about that in history classes and watching historical drama so I don't see there is anything weird about it. Harem dramas where the heroine fights other consorts in the palace is trending in my country right now. Those dramas are really depressing, tragic and bloody which make viewers despised the harem system.