2 Kings 18:5
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. 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.
Trust in the LORD God of Israel was Hezekiah's defining quality as king. That trust meant he did not depart from following God but kept the commandments commanded through Moses. It meant working what was good and right and true before God, doing every work he began with all his heart in reforms for the spiritual and temporal good of Judah.
Because of this trust the Lord was with him and he prospered. That faithfulness made him unmatched among all the kings of Judah before him or after him.