The clean-up extends beyond Judah to former Israelite territory

2 Kings 23:15-30
Then Josiah looked around, and when he saw the tombs that were there on the hillside, he had the bones removed from them and burned on the altar to defile ti, in accordance with the word of the Lord proclaimed by the man of God who foretold these things. (1 Kings 13:2)
Just as he had done at Bethel, Josiah removed and defiled all the shrines at the high places that the kings of Israel had built in the towns of Samaria that had provoked the Lord to anger. Josia slaughtered all the priests of those high places on the altars and burned human bones on them.
The king gave this order to all the people: "Celebrate the Passover to the Lord your God." Not since the days of the judges who led Israel, not throughout the days of the kings of Israel and the kings o Judah, has any such Passover been observed.
Neither before nor after Josiah was there a king like him who turned to the Lord as he did - with all his heart and with all his soul and with all his strength, in accordance with all the Law of Moses.
The clean-up extends beyond Judah to former Israelite territory. The neglected Feast of Passover is celebrated once more and private malpractices are deal with.
God's judgment is delayed but not reversed: the nation's heart is not changed by the king's reforms. Josiah dies in futile conflict with Pharaoh Necho, who was marching to join forces with Assyria after the fall of Neneveh the Assyrian capital, to the Babylonians.
Why?
King Josiah reform Judah and Israel and remove all the detestable things in his territory, but the heart of Judah and Israelite had been defiled and had turned away from the Lord.
God's judgment is delayed because of the behavior of Josiah, but the anger of the Lord is still existing for the sins of his forefathers.
How?
Even a righteous man do the right thing may get the mercy from the Lord, delay God's judgment a while but the way of the Lord will not changed.