I find three important thoughts in Judges chapter 2.
First, remember that Israel was supposed to drive out the inhabitants of the land – or kill them. Instead, she chose to let them stay and they influenced Israel for evil (just as God had said). God made a covenant with Israel, to bless her and give her the land of Canaan. But when Israel refused to be obedient to the Lord, God was under no obligation to fulfill his part of the covenant. Covenant promises are conditional.
Second, God could, of course, have driven the Canaanites from the Land (or killed them) Himself. But He chose not to do that. Instead, he used the Canaanites and their pagan attractions to test Israel, to give them an opportunity to overcome temptation and remain faithful. It was a test they failed. He also allowed the Canaanites to remain in the land so that Israel would not forget how to wage war.
Third, chapter two provides for us a summary of the story of the book of Judges. It is a constant pattern, from unfaithfulness to oppression to repentance to deliverance. The fact that God allowed the pattern to repeat for four hundred years is a testament to His grace.