Question

How did the economic trends of the 1920s help cause the Great Depression?

Answer 1

Several interpretations have been put forward

Explanation:

The artificial issuing of money(because of the Federal Reserve system introduced before WWI) led to an artificially swollen economic growth and libertarians( the Austrian school of economics) criticize this intervention and attribute the Great Depression to it (see Boom and Bust theory)
https://www.investopedia.com/terms/b/boom-and-bust-cycle.asp
For instance, Rothbard wrote about the Great depression in which he clearly accuses central banking of being responsible of the crisis of the thirties.

Monetarists have accused the federal reserve of worsening the crisis by cutting the money supply instead of growing it. Milton Friedman is the best example.

Marxists instead have pointed out overproduction as the main cause for the crisis. They claim that competition forced capitalists to squeeze down the salaries of their workers therefore undermining their purchasing power. On the other hand competition forced capitalists to invest massively and production eventually overtook consumption. In the Twenties the gap between the poor and the rich was indeed gigantic.

Keynesians make a claim quite similar by insisting on the necessity to stimulate consumption