My grandfather comments as follows: Without a doubt, Yitzchak our father had many lofty and spiritual reasons to explain his preference for Esav over Yaakov. But the Torah text states that, ultimately, this was the what motivated him, in spite of all the reasons he could provide. That is the proof to hashochad yaver eyney chachamim [bribes will blind the eyes of wise men]. Likely Yitzchak would be most disconcerted by reading in the Torah that his love for Esav was ki tzayid bepiv.
The footnote on this refers to the Midrash about 3 people in TaNaCh who might have acted differently if they had realized their actions were recorded:
R’ Yitzchak said: When a person does a mitzvah, he should do it with all his heart… Had Reuven known that Hashem would record [in the Torah] that he had saved Yosef from his brothers, he would have carried Yosef back to his father on his shoulders! Had Aaron known that Hashem would record in the Torah, “And he will see you [Moshe], and he will be joyous in his heart [without jealousy over Moshe’s appointment as leader of Israel], (Shemos/Exodus 4:14)” he would have come out to greet him with dancing and drums… Had Boaz known that Hashem would record in the Torah that he gave Ruth grain, he would have fed her fattened calves. [Rus Rabbah 5:6]
The text of my grandfather's commentary continues with a connection to chet hameraglim and chet Korach. They had achieved a very high spiritual level amid the dor dea, and it is certain that they startied out with lofty reckonings to do what they did. Nevertheless, there is no contradiction to what Chazal and the commentaries of pshuto shel mikra say that they were swayed by ego and the desire for honor. They were, in effect, bribed, and bribes blind the vision of wise men. The Torah recognizes the primary motivation that is within their souls and so it reveals it in the narrative as the root cause.
The footnote says this is along the lines of the rule that the Torah speaks about elyonim and hints betachtonim. The root of everything is its spiritual manifestation.