Class-ism is something deeply rooted into their society, King seemingly doesn't like it either but law is law and it seems that he couldn't change that law. Should still have told her first in private instead of public though.
the author likes to contradict his own message?
because pushing through the "righteousness" of the allegedly superior class is sure a turn from a protagonist becoming an outcast for being classless.
it poisons the motive.
in my opinion in would have been the better choice storywise to have lythe making the decision to support the elder princess.
they just stole the position she was educated and prepared for a lifetime.
the reward for merit policy of the other characters is nothing but lip service.