I don't think Oscar wanted to back out because of a girl. It was obvious that he was trying to help the First Prince and started protecting Carnelia when he discovered she wasn't with the Empress. My guess is that the real reason Oscar wants to back out is that he doesn't want to get revenge at the price of the country. Even if the Pariams are justified anger the Emperor, they obviously have no interest in protecting anything but themselves. The country and its people would suffer therefore Caesar would be the best choice to sit on the throne.
If this is why Oscar did what he did then it's a little sad because he already has the most important quality of a good Emperor, putting his people's needs before his own. He's already shackled to the Pariam family though.

I wanted why they wanted revenge in the first place. The King does seem like a d and to be honest. I don’t like the red guy any more than the next person but why would I give up chance of revenge cause his friend wants to back out because some chick. A chick who already married as well.