Komentarz do Diwrej ha-jamim II 30:15

and the priests and the Levites were embarrassed that they had delayed to consecrate themselves. They tarried so long and did not come until now for the following reason: they could not believe that this was true beforehand, because Ahaz had dismissed them from officiating as priests. And so they said, “Is it possible that yesterday Ahaz worshipped idols, and that his son Hezekiah, immediately in the first year and first month would tell the priests and Levites to worship the one God alone and have need of us?” They were therefore lazy and neglected to come, together with the rest of Judah, whom Ahaz had dismissed. But when they investigated and understood that everything was for the name of Heaven, they all came and consecrated themselves.