Why do historians argue that World War 1 was the legacy of World War 2?

Historians argue that World War I laid the groundwork for World War II through its unresolved political and economic issues, particularly the harsh terms of the Treaty of Versailles, which fostered resentment in Germany. The war also led to the rise of extremist ideologies, such as fascism and Nazism, as countries struggled with instability and economic hardship. Additionally, the failure of the League of Nations to maintain peace demonstrated the ineffectiveness of post-war diplomatic efforts, setting the stage for further conflict. Thus, the consequences of WWI directly influenced the conditions that led to WWII.