EXACTLY!
They were what we call "experts". Real ones. And Roosevelt, for all his other faults, was smart enough to let them run the show. The aptly named Robert Strange McNamara, for all of his exalted three years of service, was absolutely NOT an expert on running a war. Lyndon Johnson, for all of having served as a Naval Officer reaching the "high rank" of Commander, was even less an expert on running a war.
Roosevelt let the experts run the war.
Johnson ran the war with his own utter lack of expertise.
Trump is letting Hegseth and the JCS run the war.
FDR was also Assistant Secretary of the Navy during WWI.