1)
Why does it say "Rak"?
1.
Malbim: The kingdom was solid from inside [Yisrael] and outside, just there was one Chisaron in Avodas Hashem - people offered on Bamos because the Beis ha'Mikdash was not built yet.
2)
Why were people offering Korbanos on Bamos?
1.
Rashi: It was l'Shem Shamayim. The Beis ha'Mikdash was not built yet. Anyone who wanted could build a Bamah on his roof or in his Chatzer. Radak - they were permitted from the destruction of Shilo until the Beis ha'Mikdash was built.
