Who are "Bnei ha'Medinah"?
Rashi: They are Bnei Yisrael from Medinas Eretz Yisrael who ascended now from the exile to Yerushalayim.
Ibn Ezra: People of Medinas Bavel.
This recount is repeated in Nechemyah (7:6-73). Here it says "that Nebuchadnetzar exiled to Bavel." There it says only "that Nebuchadnetzar exiled them"!
Malbim (1): Here discusses the esteemed ones, who ascended from Bavel (the capitol) itself. Galus Yechanyah exiled the Sarim and greatest people to the capitol; they were always honored. Galus Tzidkiyah was to the Medinah; they were lowly in [Nebuchadnetzar's] eyes. So was Yirmeyah's Mashal of the good and bad figs (Perek 24).
Why does it mention Yehudah?
Rashi: Bnei Yehudah returned to their cities.
Refer to 2:1:4:1.
Here it says "li'Yerushalayim vi'Yhudah"; in Nechemyah (7:6) it says "li'Yerushalayim veli'Yhudah"!
Malbim: Here, primarily they returned to Yerushalayim; from there, they spread to Yehudah. The lower people primarily went to Yehudah to live. This is like I wrote on Vayikra 16:3, that when the prefix preposition is not repeated [for both nouns], the first is primary; when it is repeated, they are equal.
