As much as the prince is an asshole for it, he kinda has a point. sacrificing 1 person for the good of the entire kingdom. It doesn't seem like the saint did it unwillingly either, it's pretty easy to guess that she lied to the MC about coming back so she wouldn't go on a rampage considering her temper problem. His personality is is ass though, instead of honoring her, he just takes all the credit, like, bro, your entire downfall to to the MC could of simply been prevented by giving your fiance some shared credit