Here's my theory:
What I think a lot of people are not understanding is Alexandros(?)/the emperor killed the previous emperor (explained by the secretary in a previous chapter). He's not trying to be known as a benevolent king. He's trying to rule the country as best as he could, and that requires getting rid of the corrupt ministers. He hasn't been emperor for long, and he can't afford to be usurped by the nobilities who disagree with him. So he's trying to stay in power by making the nobilities fear him. Now, if he were to have someone who's actually kind to be the empress (like the OG Robelia), the empress might try to go against his will whenever he does something she deems "unethical" or "evil". Hence why he's looking for someone who'd understand his manipulative ways. This is probably why he doesn't like the OG Robelia, why he likes the concubine, and why he now likes the 'reincarnated' Robelia.
Comment by Nom-Nom Nami on I’ll Divorce My Tyrant Husband - Chapter 13
2 Replies
You forget the former Robelia was up to the task while the concubine isn't. Also the actual Robelia might just betray him to force the divorce, if not to eliminate him should she free herself at the price of the emperor death. Can't be ruled out that the emperor has a kink for wiskedness in women, rather than seeking "understanding" -- which (according to Alexendro's words/thoughts himself) I remember annoys him in the concubine at the end of the day.
And that's exactly why she was kept until the very end. She's getting the job done, so the emperor kept her even if he disliked her. So now the emperor has an 'ally' (concubine) that is as wicked as he is, and he has Robelia, who's doing all the empress work. The OG/Book Robelia would probably never betray the emperor because that's how she was written. That's what frustrated the 'new' Robelia. OG Robelia spent her entire life doing things for the sake of others.