Why did the great depressipn last so long?

The Great Depression lasted so long primarily due to a combination of factors, including the Stock Market crash of 1929, weaknesses in the banking system, reduced consumer spending, and high unemployment rates. These economic challenges were exacerbated by the global nature of the depression and policy mistakes made by governments around the world. It took time for economies to recover and for policies such as the New Deal in the United States to have an impact.