Gives us an overview of what is happening. Joshua is in his last days as the book starts. The people of his generation remain faithful and grateful for what God has done for them. He dies having achieved all he was promised to.
But they did not pull down the false idols. Joshua’s generation were only faithful because of a visitation by an angel and a promise before they went and claimed their lands. The root cause was still there, and its effect was insidious.
In one generation, just the children of those who fought with Joshua, they had largely rejected God and followed the local religion.
The judges are leaders, probably tribal chieftains who God blesses. Their earthly power is legal, not inherited like monarchs. They bring the people back to God. But then the people are faithless again, over and over.
God is angry with the people and leaves the foreigners there as a test and a curse. God the holy, dealing with unholy humans, often does his work though a second-best plan. This pattern of the second is throughout the bible.
I think about my own children, especially my oldest, with pain. He is so struggling with life. I’ll pray for him now.