Psalm 106:28-29 They joined themselves also unto Baal-Peor, and ate the sacrifices of the dead. Thus they provoked him to anger with their inventions; and the plague brake in upon them.
Even after the Lord delivered them and made a Covenant with them, they broke the First of the Commandments by worshipping (joining themselves to) false gods. Baal and other idols were in fact demons and the inventions of their corrupted human minds.
Idolatry, trusting in something other than the Lord God, is a grievous sin that provokes God’s jealous wrath. The Lord has placed His worth and value on and given His life to His created humans beings. To replace God alone as the source of all good is to despise Him and His love. Understandably, this releases God’s righteous wrath.
Idolatry comes in many forms and temptations present themselves in so many different ways that we don’t always recognize the sin. We are simply to look to God alone for all good, which we find impossible to do for it seems to us that good things come from the world. Jesus is the only good, and we seek first His kingdom.