One of the main causes of the WWII was the Versailles Treaty which closed WWI. It treated Germany poorly and Germans felt aggrieved. However, as the Wehrmacht rolled across Europe, the memory of the Versailles Treaty was lost in the ensuing carnage. Hitler’s military rampage destroyed any sympathetic alliances that he may have had.
Eventually the original causes of that war got smothered by the atrocities committed during the war and the accompanying genocidal actions. In the case of WWII that meant the Nazi holocaust.
