1)
Why does it say "Asher Hecheti Es Yisrael"?
1.
Malbim: He caused Yisrael to consider them proper; also Yehu continued them. Yaravam's personal sins, which Yisrael were not drawn after, also Yehu was not drawn after them.
2)
Why did he not eradicate Yaravam's golden calves?
1.
Rashi: It was amidst fear lest kingship [over the 10 tribes] return to Beis David, like Yaravam feared.
2.
Radak (30): They were made l'Shem Hashem. Even so, it was a great sin - "Lo Sa'asun Iti [Elohei Chesef vEi'lohei Zahav]" (Shemos 20:20).
