Friedman thought that government intervention often deepened economic slumps. As it happens, much of his scholarly work has discredited Keynesian economics. This presumably occurred because people's wants were satisfied. If true, it would then justify higher government spending to offset weak private spending. But by analysing historic consumption patterns, Friedman rightly showed it was not true.
People are unpredictable and almost always developed new wants.
More important was his explanation of the Great Depression. In the 1930s, Keynes had argued the private economy could drop into a deep slump from which it might not automatically recover. However, between 1929 and 1933, about 10,000 banks failed, leading to a one-third drop in the money supply and widespread bankruptcies. But Congress had created the US Federal Reserves in 1913 to prevent banking panics, Friedman and Scwartz noted. If the Fed had done its job, the Depression would have been only a normal business slump.