I haven't read this manhwa, but your the ex husband in your spoiler sounds like the white haired guy from https://www.mangago.zone/read-manga/the_way_that_knight_lives_as_a_lady/
He killed (even beheaded if i remember correctly) he female lead for his own gain, but later it was shown that he actually loves the FL (in possessive obsessive way), in that manhwa i think somehow he was the one who arranged for FL's soul to reincarnate in another body so he didn't mind to kill the original's body (because he knows the soul will reincarnate somewhere)
He also didn't have any idea which body FL reincarnated to, so he doesn't recognize FL's new body for a long time lol
The ex-husband in this manhwa is probably in similar situation
Mannnnn I don't think he loved the FL either. I think he's probably just a mad man obsessed with beautiful things or something like that. (I'm guessing he has something to do with the dissappearing women they mentioned) And with Adrienne withering away he killed her before she became too "ugly" from her sickness. That's my guess anyways. As for the prince he's just in denial but also it seems he is like a detective and the grand duchess is such a high position it is definitely possible for someone to fake her corpse or something like that. I think the prince really just wants to see if there was any foul play involved tbh. Like if she died from her sickness or if she was poisoned (which she was so he's right to investigate) plus I think that during the mourning period the body is supposed to be on display because she might a) be in a coma. Or b) had been poisoned. Signs of poisoning only show up on bodies days to weeks after death. But I do agree that the story telling is shit and this all could have been conveyed way better
I really thought it had potential, I mean the concept of the story is good. But man--most of it just does not make sense.
Like, the Ex-husband loved the FL (original body), we know his type of man. Obsessive and possessive where he would literally put his beloved in a cage and cut her legs off just so they could stay with him. He's the type that won't allow it even if his beloved asks to be killed and will force them to stay alive (barely) because of his selfishness.
At least, in my experience of reading, he's that kind of guy.
But this really threw me in a loop. He killed his wife. HE KILLED HIS BELOVED WIFE! I mean, why???!! Just why??!! What's the point??? He doesn't want to see her suffer anymore??? We know for sure he doesn't love his Mistress so why the heck did he kill his Wife when he's not doing it for the Mistress?!! Like---cut the bullsh*t, you idiot. You don't love this Mistress so why make her your next Wife by killing the original one???
It. Doesn't. Freaking. Make. Any. Sense!
Normally, if this were a different kind of guy I would somewhat understand why he would poison the wife so that she'll stop suffering. Mercy killing in a way. But holy mother of crap that's not the kind of guy this one is. He's selfish. Egotistical. Obsessive. Possessive. Manipulative son of a b*tch. I'd be damned if he wasn't any of them and I'd be damned even more if he actually did it in the act of mercy killing.
It also doesn't make any sense that the Prince wanted to confirm the FL's death, like he wanted to see the body and the Ex-husband wouldn't allow it, but it doesn't make sense that he doesn't believe the FL's dead when several people already saw her corpse in the first chapter.
The ratings speak for itself. So disappointed at the story that I forced myself to read through its 17 chapters. Anyways, it's real bad.