There are certain mid century icons who are above reproach regardless of evidence to the contrary. General George Marshall is one of those characters. He was promoted to Chief of Staff of the Armed Forces over dozens of more qualified and senior candidates even though he never had a combat command. Amazingly there was no coordinated national intelligence network existing before Pearl Harbor. Marshall's job was to coordinate the mission and strategy of the various branches of the Armed Forces but he apparently wasn't up to the job. He was one of the few who had access to the decoded Japanese transcripts, code name "Magic" and that's how he apparently spent most of his time as the de-facto intelligence chief. There is no evidence that the Chief of Staff met regularly with leaders of the various military branches in the critical months before the Attack and Marshall never emerged from his office to actually visit areas most likely to be the target of the first strike. What advice could Marshall actually offer to Kimmel and Short since he never saw a shot fired in anger himself?
Marshall was a product of the American military's 'good old boy' system same as MacArthur was, and ditto Patton, same as Hitler's High command, same as Britain's, same as Stalin's. It was also Patton's 'good old boy' influence that got Eisenhower leap-frogged to his top job, over MacArthru's whining, so it worked both ways; some of the 'good old boys' were in favor of recognizing talent, some where out for themselves. 'Meritocracies' don't seem to do any better at producing competent leaders, though, due to the 'Peter Principle' and other reasons; at least with the 'good old boys' the competent can get bumped to the top jobs far sooner than they ever would via a 'meritocracy' slog. And who defines what 'merit' is is also a unknown in itself. A quartermaster sergeant who has never been 'shot at' has a better grasp of how to move an Army or Navy than a combat sergeant who has been' shot at' a hundred times. Logistics is king in modern warfare, and it most certainly was in WW I and WW II, not how many people one stabbed with a bayonet in the trenches.
Was Marshal truly awful? The evidence is both Japan and Germany were rubble in less than four years, despite being thousands of miles away, and we kept ourselves and all of our allies in the war on four fronts. So who were the most incompetent and had the worst intelligence? Not the U.S., which is immediately obvious.