1)
How did they anger Hashem with Bamos?
1.
Radak: They offered to idolatry on them in the days of Eli and Shmuel, until Shmuel returned them to the good path after the Aron was returned from Sedei Pelishtim.
2.
Malbim: This is like it says "Hem Kin'uni v'Lo Kel Ki'asuni b'Havleihem" (Devarim 32:21) - Hashem was angry with their folly and the Bamos that they made to their folly.
2)
What was Hashem's envy?
1.
Malbim: They switch Avodas Hashem for Avodah of idols and a non-god.
