Josiah got rid of all the disgusting idols throughout Israelite territory. He made all people found in Israel serve the Lord their God. As long as he lived, they didn’t stop following the Lord God of their ancestors.
The king was overjoyed and had Daniel taken out of the den. When Daniel was taken out of the den, people saw that he was completely unharmed because he trusted his God.
They left us. However, they were never really part of us. If they had been, they would have stayed with us. But by leaving they made it clear that none of them were part of us.