How does the US move from a free market economy to a mixed market economy? Please do not hesitate to ask! Thanks!

At the beginning of the 20th century, because of the big capitalists in the free market economy, a large amount of resources and products hoarding, so it led to the market drastically deviated from the perfectly competitive market, resulting in the Great Depression of 1929 (The Depression). And after that, Americans reflected on the history and after almost every period of time, there was a massive economic shock. After that, economist Keynes's theory of macro-control was gradually emphasized, which weighed the government's intervention in the market and the basic principle of free allocation of the market economy. Up to this point, the U.S. economic system gradually transformed like a mixed market economy. Until the 1960s, the mixed market economy has been carried out in an orderly and effective manner, which also led to Marx's economic theory of "capitalism will certainly go to extinction because of the imbalance in resource allocation" inference was overturned, and is also known as "the second spring of capitalism" by most of the Marxian economists. ".