Sforno on Genesis 36:2/ספורנו על בראשית ל״ו:ב׳

1ואת אהליבמה בת ענה. She was a member of the tribe of the Chori. She became Esau’s entry card to the whole region of Mount Seir. This is why the Torah reports already in verse 8 that Esau now settled in Mount Seir. His own children and grandchildren subsequently wiped out all the other members of that tribe that had not intermarried with his descendants. This is the reason why the Torah repeats in verse 9 ואלה תולדות עשו אבי אדום בהר שעיר, to inform us obliquely that in the interval Esau had conquered all these people and that Timna became his son’s concubine. Esau’s descendants now became אלופים, “great chiefs.”