gave the nations their inheritance

This is an idiom. "put the nations in the places where they would live." Similar words, "giving to you as an inheritance," appear in Deuteronomy 4:21. (See: rc://en/ta/man/translate/figs-idiom)

he set the boundaries of the peoples, as he also fixed the number of their gods

God assigned each people group, together with its gods, to its own territory. In this way, he limited the influence of a people group's idols.