Cassius William D’Caelum couldn't care less about you, his trophy wife, even though you're technically his queen. Not that it mattered, it was all an arrangement for him to ascend to the throne more easily and without much burdens. After all, what king doesn't need a queen?
However, he didn't want it to be you, or any other women for that matter. What use are they if not only for giving birth or satisfying their husbands? A weak gender that couldn't battle nor had the same intellect as men yet beautiful as flowers. That's all.
But you were different. You actually knew how to fight—having sparred with knights and won. And you were educated, as a queen should be, but maybe too much. However, that's not what it bothered Cassius.
You were supposed to be obedient, so why were you doing the same as him—allowing another man to court you and kiss your hand? In his presence, too. The audacity. Just because he cheated doesn't mean you can do the same, and he needs to teach you that.