The key factor in the rise of totalitarian regimes in the 20th century was the combination of economic instability, social discontent, and political unrest following World War I. Many nations faced severe economic depression, unemployment, and a loss of faith in democratic governance. Leaders who promised stability, national rejuvenation, and solutions to these crises, such as Adolf Hitler in Germany and Benito Mussolini in Italy, capitalized on this discontent. They established authoritarian systems that suppressed dissent and promoted aggressive nationalism, enabling them to consolidate power and reshape society according to their ideologies.