Albert Barnes Commentary 2 Kings 21:24

"But the people of the land slew all them that had conspired against king Amon; and the people of the land made Josiah his son king in his stead." — 2 Kings 21:24 (ASV)

The intention of the conspirators had perhaps been to declare a forfeiture of the crown by the existing line and to place a new dynasty on the throne. The people would not tolerate this. They arrested the conspirators, put them to death, and insisted on investing the true heir of David, the eldest son of Amon, with royal authority, though he was only eight years old.