As Josiah continued his restoration of the true religion and worship of Yahweh God, he destroyed the high places where priests offered sacrifices to their idols, but then the Bible says,

Nevertheless the priests of the high places did not come up to the altar of the Lord in Jerusalem, but they ate unleavened bread among their brethren (2 Kings 23:9).

Those priests could not see that their false religion was on its way out, and so they refused to worship the Lord in Jerusalem, although it appears they made some accommodations by eating unleavened bread with their brethren, unless that was a continuation of their idolatry.