Why did they offer these Korbanos?
'Rashi': It was a Hora'as Sha'ah. Malbim - the bulls and goats were like Par Helam Davar for idolatry - however, then the bulls are Olos, and not Chata'os 1 . They brought only for seven Shevatim, for Gad, Reuven, Chetzi Menasheh, Zevulun and Naftoli were already exiled; it was as if all of Menasheh was exiled. Shevatim that did not sin, they bring along with those who sinned, but only if they are in Eretz Yisrael. The rams and lambs were Nedavah.
Malbim (22) explains that the bulls were Olos; "Chatas" applies only to the goats. A support is verses 22-23, which discuss all four kinds, and only the goats are called Chatas. A Hora'as Sha'ah was needed only for them. (PF)
Why does it say "Al ha'Mamlachah v'Al ha'Mikdash v'Al Yehudah"?
Radak: They needed to atone for all of them.
Malbim: It was considered a mistake ruling of the Sanhedrin, for people did not protest against Achaz 1 .
This does not explain "Al ha'Mikdash"! Also, Achaz was Mezid! Also people did not protest, amidst consent for idolatry, or fear! Perhaps they erred to think that Piku'ach Nefesh permits offering to idolatry. (PF)
Why does it say "Al Mizbach Hashem"?
'Rashi': They did not offer on the Mizbechos that his father Achaz made.
