Who were "Kohanei ha'Bamos"?
Radak: Their paternal lineage is from Aharon. Targum Yonasan says Kumaraya, because they had become priests to idolatry. Yoshiyah brought them to Yerushalayim and led them to repent.
Malbim: Most Bamos were for Shamayim (just it was forbidden to offer on Bamos after Shlomo built the Beis ha'Mikdash). Or, they offered to Hashem and idolatry. The Kohanim were able to tell where all the Bamos were.
What is the meaning of "va'Ytamei"?
Radak: He made [the Bamos] a place of Tum'ah, to cast there Neveilos and all Tum'ah, to distance idolatry from the hearts of the nation. Malbim - he did not destroy them, for most were l'Shem Shamayim. 1
We must say that the Bamos of the gates were l'Shem idolatry. (PF)
What is the meaning of "Asher Pesach Sha'ar"?
Radak: This is like va'Asher Pesach ha'Sha'ar. We find like this (that the prefix Vov is omitted) - "Shemesh Yare'ach" (Chabakuk 3:11). I.e. he destroyed the Bamos of the gates, and also the Bamah at the opening of Sha'ar Yehoshua, the mayor. Perhaps it was bigger than the other Bamos, therefore it is mentioned by itself.
Why does it say "Asher Al Smol Ish b'Sha'ar ha'Ir"?
Radak, Targum Yonasan: It was to the left of a person who enters the gate of the city.
