Judges 2:20
And the anger of the LORD was hot against Israel; and he said, Because that this people hath transgressed my covenant which I commanded their fathers, and have not hearkened unto my voice; And the anger of the LORD was hot against Israel; and he said, Because that this people hath transgressed my covenant which I commanded their fathers, and have not hearkened unto my voice;
The anger of the Lord burned hot against Israel because this people had transgressed the covenant commanded to their fathers and had not hearkened to his voice. The transgression was their repeated return to idolatry after their deliverers died. The covenant judgment that followed was that the Lord would no longer drive out the nations which Joshua had left.