Deuteronomy 29:24-26

then all the nations will ask, 'Why did ADONAI do this to this land? What is the meaning of such frenzied, furious anger?'

People will answer, 'It's because they abandoned the covenant of ADONAI, the God of their fathers, which he made with them when he brought them out of the land of Egypt.

They went and served other gods, prostrating themselves before them, gods they had not known and which he had not assigned them.