#spitefulchant

so he went to Ishmael and married Mahalath, the sister of Nebaioth and daughter of Ishmael son of Abraham, in addition to the wives he already had. 

This looks to be an attempt to spite his father for giving the birthright to Jacob. Despite it being an accident, Esau seems to be against forgiving his father. Missing out on something that he expected could be weighing on his psyche. Esau may look to be somewhat like a rebel, from this point.