Israel had forgotten its covenant God, and made covenants with the inhabitants of Canaan. It was on account of their disobedience that God would refuse to drive out the Canaanites, which otherwise God himself would have accomplished. “In other words, the process of dispossession and occupation would have been completed in due course if the Israelites had fulfilled their obligations to Yahweh, but now their disobedience has put the completion of the Conquest in jeopardy (Judges 2:3)."1
3 So now I say, I will not drive them out before you, but they shall become thorns in your sides, and their gods shall be a snare to you.”