27 Israel did get to take the livestock and loot left in the city; God's instructions to Joshua allowed for that.

Matthew Henry's Commentary on Joshua 8:27

Commentary on Joshua 8:23-29

(Read Joshua 8:23-29)

God, the righteous Judge, had sentenced the Canaanites for their wickedness; the Israelites only executed his doom. None of their conduct can be drawn into an example for others. Especial reason no doubt there was for this severity to the king of Ai; it is likely he had been notoriously wicked and vile, and a blasphemer of the God of Israel.