I don’t think I ever heard about this in school. I don’t know who came up with it first – the same wording is rampant in a Google search – but here it is from the “Timeline of the Great Depression.”
Alarmed by Roosevelt’s plan to redistribute wealth from the rich to the poor, a group of millionaire businessmen, led by the Du Pont and J.P. Morgan empires, plans to overthrow Roosevelt with a military coup and install a fascist government modelled after Mussolini’s regime in Italy. The businessmen try to recruit General Smedley Butler, promising him an army of 500,000, unlimited financial backing and generous media spin control. The plot is foiled when Butler reports it to Congress.