Chapters 17-23 tell of some other kings of Judah. We are also told of Athaliah, whom we read about in 2 Kings 11. She tried to kill all of her grandsons so she could seize the throne. She doesn’t know Joash survived, so he becomes king at age 7. Not surprisingly, Joash is not ready to reign on his own and is mentored by a priest named Jehoiada. Joash does well while his mentor is alive, but turns against God when Jehoiada dies. Joash goes even as far as killing the son of his loyal mentor.
There is a difference between character and behavior. Apparently Jehoiada had successfully influenced Joash’s behavior, but not his character. If a person does the right thing because they don’t want to be punished for doing the wrong thing, that’s good behavior, but not good character. Good character does the right thing because they want to. Do you look good on the outside, but inside desire to do the wrong things? Do you behave differently when there is no chance of getting caught? If so, ask God to change your character (Galatians 5:22 & 23). Just behaving better isn’t enough.