Why did God allow the Israelites to be captured or enslaved in the Old Testament?

When the nation of Israel turned away from God then He allowed them to be conquered by other nations.

Israel had the choice, to obey God and be blessed or disobey God and be cursed:

Deuteronomy 11:26-28 "Today I am giving you the choice between a blessing and a curse---

a blessing, if you obey the commands of the LORD your God that I am giving you today; but a curse, if you disobey these commands and turn away to worship other gods that you have never worshiped before

Israel disobeyed God:

Judges 2:11 - 14 Then the people of Israel sinned against the LORD and began to serve the Baals.

They stopped worshiping the LORD, the God of their ancestors, the God who had brought them out of Egypt, and they began to worship other gods, the gods of the peoples around them. They bowed down to them and made the LORD angry. They stopped worshiping the LORD and served the Baals and the Astartes. And so the LORD became furious with Israel and let raiders attack and rob them. He let the enemies all around overpower them, and the Israelites could no longer protect themselves.