Does the Torah suggest that somehow Isaac and Rebecca had a hand in the tension between their children? How could Isaac get it so wrong that he favoured the villain of the piece?

While Esau’s hunting prowess is given as justification for Isaac’s love, no reason is given when we are told that Rebecca loved Jacob.  

The 12th-century commentator Radak says that, of course, Isaac loved goody-goody Jacob. Quite literally, that went without saying. The Torah’s focus is Isaac’s surprising love of Esau and reluctance to write his son off.
 
While Esau is vilified by tradition as a wayward child, he nonetheless found an avenue which made his father proud, honouring him by bringing the delights of the hunt.

By contrast, Rebecca’s love for Jacob is unqualified.  She had every reason to love him, and none not to.  This was bolstered by the prophecy that God had given her during pregnancy that the elder would eventually serve the younger. Isaac represents hope in the leadership qualities he perceives. Rebecca represents faith in the leadership she anticipates.  

On close reading “Isaac loved Esau” (in the past tense) contrasts with the Hebrew “Rebecca loves Jacob” (in the present). Isaac’s imagination that leadership was synonymous with force and glossing over Esau’s deficiencies elicited love that existed but elapsed. Rebecca’s love, rooted in her faith in Jacob’s noble qualities, is a love which exists and endures. 

Our Torah gives us patriarchs and matriarchs who are real people with real hopes, faults and flaws. If our biblical forebears were only all good or all evil, they would be like Goldilocks’ three bears — fairy-tale characters with nothing much to teach.

We should look for the positive in people but not blind ourselves to their flaws. Though love can’t necessarily be explained, from Rebecca we learn that when our love is a love of virtue, that love lives on.  

We might know that we love our family so much, it goes without saying. Radak’s commentary is an explanation but not an affirmation.  If we love them, we should tell them, even so