Responses
He took her for granted, and his ego couldn't handle it when he realized that she doesn't love him. He's insecure, like all narcissists and can't handle the fact that the person which he used as a doormat disappeared, mainly because he doesn't think that he'll ever be able to find another one that would be willing to completely put down themselves to earn his "love" and feed his narcissism. It's basically obsession, with himself mostly.

...didnt the prince hate Iris? Why is he suddenly so sad for her and feels so much empathy, even concern because she loved him a lot? That's...confusing, I just wonder what made them suddenly or moreso finally see her as a living being?