See of this 2 Kings 1:1. It is here repeated to make way for the following story. Ahaziah did not attempt the recovery of Moab, either because he was a man of a low spirit and courage; or because his sickness, or the shortness of his reign, gave not opportunity for it.
Related Commentaries of 2 Kings 3:5
2 Kings 3:5
5 But it came to pass, when Ahab was dead, that the king of Moab rebelled against the king of Israel.