Causes of the Great Depression
Second, there are the monetarists, who believe that the Great Depression started as an ordinary recession, but that significant policy mistakes by monetary authorities (especially the Federal Reserve) caused a shrinking of the money supply which greatly exacerbated the economic situation, causing a recession to descend into the Great Depression. Related to this explanation are those who point to debt deflation causing those who borrow to owe ever more in real terms.
The Commanding Heights
The Great Depression caused massive unemployment and with it massive public distrust of corporations and wealthy individuals. In response, the New Deal instituted by Franklin D. Roosevelt went into effect with massive public support. Many lawyers and economists influenced by Keynes worked under the New Deal and believed that free markets would lead to disaster without proper regulation.