Why did God allow Israel to be conquered?

Answer: They worshiped other gods

All this happened because Israel had sinned against the LORD, who brought them out of Egypt, and had worshiped other gods.

“All this happened because the people of Israel had sinned against the LORD their God, who had brought them out of the land of Egypt from under the hand of Pharaoh king of Egypt. They had worshiped other gods”— 2 Kings 17:7 (BSB)