Why are questions on the causes and solutions for the Great Depression controversial today

The Great Depression was the largest economic crisis in the history of capitalism, which took place between 1929 and 1933 and affected virtually all countries and practically all sectors of the economy.  It is traditionally assumed that the crisis appeared in the United States after the so-called Black Thursday on October 24, 1929, when, according to preserved information, the prices of virtually all shares fell sharply, entailing a chain of bankruptcies and debts that gradually spread to almost all countries.

The effects of the crisis were mitigated by the New Deal, a program of economic and social reforms (involving the employment of the unemployed in state-led investments) introduced by President Roosevelt; the economic doctrine of Keynesianism assuming state intervention in the economy gained popularity at that time which for many years then dominated in the theory and practice of the economy of capitalist countries.

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