1)
Why is the Nevu'ah of the fall of Har Se'ir here?
1.
Radak: It is put next to the salvation of Yisrael, for then will be the fall of Edom like it says in Nevu'as Ovadyah (1:21) "v'Alu Moshi'im b'Har Tziyon Lishpot Es Har Esav."
2.
Malbim: The return of Yisrael's captivity and the Churban of Edom, who exiled them from their land, should be adjacent. When [Yechezkel] saw the return of Yisrael, he saw also the Churban of Bayis Rishon; Edom rejoiced over this. Their punishment was via Nebuchadnetzar, and afterwards via Hurdos; they destroyed [Edom's] land. However, it was not permanent Churban.
