
one reason. he's a man. Men in this time period were allowed to do whatever with how ever many women they wanted but women couldn't do the same or they'd be known as sluts. It isn't uncommon for men (espically royalty) to blatantly cheat. Kings/emperors often have a lot of concubines/misstrisses aside from the woman they're married to. So whilst he's the one walking around being flirty with another woman in public, it's lesian who'll be ridiculed as not being enough despite them just now being engaged. Marriage is just a way for fathers/men to sell off their daughters. That's why he has no choice but to marry lesian to the crown prince. the other girl was already married and divorced so that makes her "less valuable". Women are viewed as property and not people. that's also why the duke couldn't recruit her for the imperial guard despite wanting to (she's a woman).
If she is his fiancé... how can he blatantly get away with cheating in broad daylight.. he flirting and being with that chick..
And he dares to judge her????? If you want the other girl so bad go bone her and marry her.