The final plague that results in the complete and immediate liberation of Israel from Egypt is the death of the firstborn across the entire land. God says this is ultimately judgment on the gods of Egypt which in turn is poured out on those who have followed those gods in open rebellion against YHWH. But something interesting happens when the nation of Israel is released and many Egyptians change allegiance. This happens in large part due to a complete deconstruction of their own culture and theology in light of the true God.