What does Genesis 28:8 mean?

Here begins a thought that will be completed in verse 9. Esau, apparently, had not realized that his choice to marry two Canaanite women did not please his father. This is in spite of Genesis 26:34 indicating that these women made life bitter for Rebekah and Isaac. Later, Rebekah told Isaac that they caused her to hate her life (Genesis 27:46). Some of this might have been exaggeration on Rebekah's part, since she seems mostly concerned that Jacob flee from his jealous brother's murderous rage (Genesis 27:41).

We don't know whether or not Isaac failed to communicate to Esau that he should not marry Canaanite women. Perhaps he had, and Esau simply rebelled against that direction from his parents. Scripture does not say for sure. In any case, the light seems to dawn for Esau when he hears of Isaac's command to Jacob not to do as Esau had done. One way or another, Esau seems not to have known just how burdensome his parents found his wives. Or, he had not been sensitive enough to pick up on the clues. Given his rash nature (Genesis 27:29–34), this would not be surprising.