Commentaire sur La Genèse 28:8

וירא עשו כי רעות בנות כנען, Esau realised that the Canaanite daughters were displeasing in the eyes of his father. The Torah tells us here that Esau's only concern was the effect his Canaanite wives had on his father's sensibilities. The fact that these women were evil by nature did not bother him. His soul did not despise them. Subsequent events teach that the fact that Isaac disapproved of these women did not produce any results other than that Esau did not marry still more Canaanite girls. He did not consider divorcing these wives. Perhaps Esau's only concern was that his father's blessing would not be applicable to children born to him by his Canaanite wives, and that is why married a daughter of Ishmael to insure that his father's blessing would remain effective for his descendants.

וישמע, Esau also heard that Yaakov had obediently followed his father’s instructions to get himself a wife from that far away He “saw” now that רעות בנות כנען, that the daughters of the Canaanite whom he had married were considered as evil in the eyes of his father Yitzchok. Even though he had been fully aware of this already previously, seeing that his father had already protested his marrying these girls at the time, he had not made it a major issue to forbid him to marry them as he knew that his major seed would not be Esau. Now Esau realised how deeply his father resented these daughters-in-law seeing he had sent Yaakov such a long way to get himself a wife from Charan. This is why he went to Ishmael.