Albert Barnes Commentary 2 Chronicles 34:30

"And the king went up to the house of Jehovah, and all the men of Judah and the inhabitants of Jerusalem, and the priests, and the Levites, and all the people, both great and small: and he read in their ears all the words of the book of the covenant that was found in the house of Jehovah." — 2 Chronicles 34:30 (ASV)

The writer of Chronicles has characteristically substituted “Levites” for the “prophets” mentioned in 2 Kings 23:2. While Josiah was undoubtedly accompanied by priests, prophets, and Levites, the writer of Kings thought it was enough to mention only the first two, merging the Levites with the rest of the people. The writer of Chronicles, on the other hand, considers the presence of the Levites too important to be omitted, and since the prophets were likely few in number, he passes them over.