Joash has to be the most baffling king Judah ever had. For the life of me, I just cannot fathom why he would have done the things he did.
Here's a little background: Jehoram was the son of Jeshoshaphat and he was married to Athaliah, daughter of Ahab of Israel.
2 Kings 8:16 And in the fifth year of Joram the son of Ahab king of Israel, Jehoshaphat being then king of Judah, Jehoram the son of Jehoshaphat king of Judah began to reign. 17 Thirty and two years old was he when he began to reign; and he reigned eight years in Jerusalem. 18 And he walked in the way of the kings of Israel, as did the house of Ahab: for the daughter of Ahab was his wife: and he did evil in the sight of the Lord.
After Jehoram came Ahaziah:
2 Kings 8:26 Two and twenty years old was Ahaziah when he began to reign; and he reigned one year in Jerusalem. And his mother's name was Athaliah, the daughter of Omri king of Israel.
Omri was actually the father of Ahab, so this bit does make sense.
Anyway, after Ahaziah was murdered, Athalia killed all of Jehoram's other children and took the throne for herself. Only Joash (later referred to as Jehoash) Ahaziah's infant son was saved. He was about a year old, since he was hidden in the temple for six years and then crowned king by Jehoiada the priest when he was seven.
2 Kings 11:1And when Athaliah the mother of Ahaziah saw that her son was dead, she arose and destroyed all the seed royal. 2 But Jehosheba, the daughter of king Joram, sister of Ahaziah, took Joash the son of Ahaziah, and stole him from among the king's sons which were slain; and they hid him, even him and his nurse, in the bedchamber from Athaliah, so that he was not slain. 3 And he was with her hid in the house of the Lord six years. And Athaliah did reign over the land.
4 And the seventh year Jehoiada sent and fetched the rulers over hundreds, with the captains and the guard, and brought them to him into the house of the Lord, and made a covenant with them, and took an oath of them in the house of the Lord, and shewed them the king's son.
17 And Jehoiada made a covenant between the Lord and the king and the people, that they should be the Lord's people; between the king also and the people. 18 And all the people of the land went into the house of Baal, and brake it down; his altars and his images brake they in pieces thoroughly, and slew Mattan the priest of Baal before the altars. And the priest appointed officers over the house of the Lord. 19 And he took the rulers over hundreds, and the captains, and the guard, and all the people of the land; and they brought down the king from the house of the Lord, and came by the way of the gate of the guard to the king's house. And he sat on the throne of the kings. 20 And all the people of the land rejoiced, and the city was in quiet: and they slew Athaliah with the sword beside the king's house. 21 Seven years old was Jehoash when he began to reign.
2 Chronicles 22 actually gives more detail on this.
Okay, so Joash/Jehoash was raised in the temple for six years by Jehoiada the priest. Then Jehoiada gathered all the priests and Levites from all over Judah together along with an army and declared Joash king. After that, they went out and killed Athaliah. 2 Kings 12 and 2 Chronicles 24 detail how Joash ordered the priests to collect money to repair the temple and then REBUKED the priests, including Jehoiada, for collecting the money but not doing anything with it! He finally lit a fire under them and got the job done.
Now here's the bit that absolutely blows my mind:
2 Chronicles 24:15 But Jehoiada waxed old, and was full of days when he died; an hundred and thirty years old was he when he died. 16 And they buried him in the city of David among the kings, because he had done good in Israel, both toward God, and toward his house. 17 Now after the death of Jehoiada came the princes of Judah, and made obeisance to the king. Then the king hearkened unto them. 18 And they left the house of the Lord God of their fathers, and served groves and idols: and wrath came upon Judah and Jerusalem for this their trespass. 19 Yet he sent prophets to them, to bring them again unto the Lord; and they testified against them: but they would not give ear. 20 And the Spirit of God came upon Zechariah the son of Jehoiada the priest, which stood above the people, and said unto them, Thus saith God, Why transgress ye the commandments of the Lord, that ye cannot prosper? because ye have forsaken the Lord, he hath also forsaken you. 21 And they conspired against him, and stoned him with stones at the commandment of the king in the court of the house of the Lord. 22 Thus Joash the king remembered not the kindness which Jehoiada his father had done to him, but slew his son. And when he died, he said, The Lord look upon it, and require it.
How could he just forsake God that quickly, start worshiping idols and then turn on Jehoiada's family like that? Like I said, it just blows my mind how someone could so completely turn around like that. It makes NO sense.