Charles Ellicott Commentary 2 Chronicles 22:1

"And the inhabitants of Jerusalem made Ahaziah his youngest son king in his stead; for the band of men that came with the Arabians to the camp had slain all the eldest. So Ahaziah the son of Jehoram king of Judah reigned." — 2 Chronicles 22:1 (ASV)

THE SHORT REIGN OF AHAZIAH (2 Chronicles 22:1–9).
(Compare to 2 Kings 8:25–29.)

And the inhabitants of Jerusalem. — 2 Chronicles 21:11; 2 Chronicles 21:13.

Made Ahaziah ... king. — This variation from the usual formula—“And Ahaziah his son reigned in his stead”—has been supposed to indicate that the succession was disputed, with either Athaliah, the queen-mother, or Jehoiada, the high priest, opposing it. It is more likely that the difference of expression simply points to the use of a different source by the writer.

The band of men that came with the Arabians to the camp. — The Hebrew is obscure for lack of further details. “The troop that came among the Arabs to the camp” appears to have been some party of half-savage warriors who, after the Jewish camp had been stormed by the invaders and the royal princes taken prisoners, fell upon and slew their captives. (Compare to 2 Chronicles 21:17; and Judges 8:18 and following; 1 Samuel 15:32.)

All the eldest. — Hebrew: the former (rîshonîm). Syriac: “For all the elder the troop had destroyed them, for the Arabs came and destroyed the camp of Israel.”