After the onset of the Great Depression, many economists radically changed their views and adopted Keynes’ “revolution,” which was not a revolution but merely a resurrection of mercantile economics. Mainstream economists don’t understand that because they don’t take economic history in school. Keynesian economics dominated until the stagflation of the 1970’s.
Responding to their mistakes of the 70s, mainstream abandoned paleo-Keynesian economics and the profession split into the New Keynesian, monetarist and neo-classical schools of macroeconomics, though hard-to-kill paleo-Keynesian econ lives on in the writings of Nobel Laureate Paul Krugman. The three new schools rejected Keynes’ idea of having the state micromanage the economy through fiscal policy because they recognized it suffered from the three lags, cogitation, formulation and implementation. In other words, the state always shows up late to the economic “accident” because it’s slow to recognize the problem, slower to formulate policy and tardy in implementing the policy. As a result, fiscal policy tended to make things worse.