Man, they’re really not buying that zenjirou is committed to one woman. Like he’s from a different world so they should know he has different standards. But i guess royal society trumps that.
Its more like, it doesn't matter how devoted Zenjirou is to Aura. Its clear from the way he has been presenting himself that, so long as they don't push him too far, Aura makes the final decision and her decision making is from the position of a monarch. Given that Aura accepted Freya, it is clear that so long as the marriage provides the kingdom adequate benefits, Zenjirou's feelings are easily ignored.
Now, they don't know if a second concubine would constitute "going to far" but it is a minor risk considering the benefits from their standpoint.