a conspiracy of priests

Then they brought out the king's son and put the crown on him and gave him the testimony. And they proclaimed him king, and Jehoiada and his sons anointed him, and they said, "Long live the king."
2 Chronicles 23:11

This was a coup d'etat led by a conspiracy of priests. But it was all proper and good. Joash was the only surviving member of the Davidic royal line. The wicked queen Athaliah had seized control of the throne in Judah. She quickly moved to wipe out all the Davidic line, but Joash was hidden in the temple as a baby, just yards from the palace where the pagan queen usurped the throne.

Really, the irony in this story is amazing. Athaliah lived in treachery and ruled with tyranny. Yet she was so pagan that she never set foot in the temple of God which stood adjacent to the royal palace in Jerusalem. She never attempted to destroy the temple (perhaps it stood as too strong a symbol of ethnic identity). So while she raged against God and abused Judah, God was quietly working his plans against her as Jehoida the high priests raised the infant prince in the secure secrecy of the temple. There young Joash was kept alive and instructed in the Law of God.

When the priests finally had enough political momentum to confront Athaliah, Joash was just a mere child of seven. But the day came where the priests armed themselves and the people assembled at a convocation to crown young Joash in coronation. With great dramatic irony, Athaliah runs to the scene only to cry out "Treason"! But she is met with the swords of the temple guard. She is executed and young Joash is placed back on the throne of David in Jerusalem. This combination of human bravery, planning, and sovereign divine providence led to poetic justice. I love it when God makes His plan come together!