Verses 1-21
End of Jezebel's Baalism in Judah (11:1-21)
Ahaziah, king of Judah, had been assassinated the day of Jehu's revolt (see 9:27). His mother Athaliah showed herself a true daughter of Jezebel when she killed all her grandchildren (except one who escaped), seized the throne, and established her mother's Baalism in Judah. The one who escaped was the baby Joash, who was rescued by his aunt (a princess married to the high priest; 2 Chronicles 22:11) and hidden for six years in the temple (11:1-3).
When Joash was seven years old, the high priest Jehoiada, with the support of the palace and temple guards, claimed the throne for him. The coup was planned for a sabbath day, when the changing of the guard ensured that a much larger group of guards than usual would be at the temple (4-8). All went according to plan without bloodshed, apart from the execution of Athaliah (9-16).
Because Athaliah had interrupted the line of Davidic kings, the restoration of the Davidic king to the throne was accompanied by a renewal of the covenant. All Jerusalem celebrated the great day. The people went wild with joy, destroying Athaliah's Baal temple and all that belonged to it (17-21).