In 2 Kings 3:27, the armies of Israel, Judah, and Edom abandoned the siege of Kir-hareseth, the capital of Moab, just as they were about to win the war because "there came great wrath against Israel", but it doesn't say who was angry nor why. I suspect it was the men of Judah and Edom who were angry at Israel.

This wasn't really Judah's or Edom's fight. They were there to support Israel as allies. When they witnessed the Moabite king sacrifice and burn his own son and heir on the city walls, I believe they had a change of heart. They had come to punish Moab for not sending annual tribute to the King of Israel, not to commit genocide.

When the rank and file of the allied armies saw just how close the Moabites were to complete annihilation, they might have become angry at Israel for how much blood they had been made to shed with no usable land to occupy and no loot that they would be allowed to take back.