On July 1, 1933, Butler met with MacGuire and Doyle for the first time. FDR was already president when the JP Morgan inspired Business plot coup was being planned.
They wanted MacArthur because he would have easily gone along with a fascist model and a coup. But he was radioactive with veterans after he attacked the bonus marchers with cavalry using flats of swords, tanks, and vomit gas.
So they went to Butler who they thought might play ball.
Instead, he exposed them. And remember, at that time Mussolini and his fascism was considered the modern marvel and more than a few admired that approach.