Why is the daughter of Matred referred to as "Bas Mei Zahav"?
Rashi: Because her father was so wealthy that gold meant nothing to him (it flowed like water).
Targum Onkelos: He was a refiner of gold (melting it like water).
Targum Yonasan: He worked in trapping animals, 1 from which he became exceedingly rich. From the proceeds, he purchased a lot of property, and became very vain, and went around boasting 'What is silver, what is gold!'
Moshav Zekenim: It teaches that all 2 of them were Mamzerim. How can Meheitve'el have two fathers? We must say that one was her father, and he fathered her through someone else's wife 3 (and people mistakenly attributed the daughter to her mother's husband).
See also Na'ar Yonasan.
How do we learn that all were Mamzerim? Perhaps only she was! (PF)?
Oznayim la'Torah: We find that Esav 'broke the fence that the nations built' after the Flood, not to indulge in adultery and in incest. Already in his teens, he had relations with a betrothed girl, and throughout his life he took women from their husbands. In fact, that is why he declined to be circumcised - since Milah is a fence against Zenus, which went against his core desires.
Why is the death of the last king, Hadar, not recorded?
Peninim mi'Shulchan ha'Gra, Malbim (to Divrei ha'Yamim I 1:43): Because he lived in the days of Moshe and had not yet died when the Torah was written. 1
It is however, recorded in Divrei ha'Yamim (I 1:47, albeit by the name 'Hadad'), because the author of Divrei ha'Yamim was Ezra, by whose time he had already died.
