There are two independent stories interwoven in Parshat Toldot. It is beautifully explained here, and it is no doubt true. I think, though, that there is a message behind it.
It starts with the passage of Bereshit 17, the Brit Mila of Avraham, which is an obvious addition and therefore not in the Torah Kedumah. The important message of the story is that Yitzchak, still unborn, is to be the promised seed of Avraham. And Yitzchak includes Edom/Esav.
The next passage is Bereshit 23, also not in the Torah Kedumah. The passage has the purchase of Ma'arat HaMachpela, at the time of the death of Sarah. The seller is Ephron, the Chittite. The important message of the story is that the Chittites are not so bad.
And then we see Esav marrying Chittite women, and we read Bereshit 28:1-9, again not in the Torah Kedumah, at the end of which Esav marries a woman of the seed of Abraham. Edom, we see, is not so bad after all.
During Bayit Sheni there was a merge of Yehudah/Israel and Edom. The above stories seem to come from Edom. They are not from Israel.
