After him was none like him - The same is said of Josiah (marginal reference). The phrase was probably proverbial, and was not taken to mean more than we mean when we say that such and such a king was one of singular piety.
Related Commentaries of 2 Kings 18:5
2 Kings 18:5
5 He trusted in the LORD God of Israel; so that after him was none like him among all the kings of Judah, nor any that were before him.