2 Kings 14:5 - Joseph Benson’s Commentary on the Old and New Testaments

As soon as the kingdom was confirmed, he slew his servants, &c. It is implied in this, that his father's murderers continued to be men of weight and interest at court, even after they had perpetrated that crime; for Amaziah retained them in his service for some time, nor durst venture to execute justice upon them till he was well settled in his authority. Probably the act they had done was in some sort approved by the generality of the people, to whom Joash had made himself hateful by his apostacy to idolatry, and his ingratitude to the house of Jehoiada.