Because God is just and justly punishes evil doers, repeated sins bring repeated judgments. The cycles found in the book of Judges is a good example of this. The Prevailing Theology of a Nation Determines the Current of Its History. If all history is covenantal, this is naturally the case. The most influential factor in understanding a nation's history is its faith.
All men are theologians.
They may be heretical theologians, but they are theologians nonetheless. Everyone has a view of God and man, of truth and duty. Nations, therefore, have predominant theologies which determine their economics, politics, commerce, ethics, traditions, laws, and all else. But if there is one thing largely overlooked by secular historians it is this factor. It is important that we understand why historians think in this way.