Well the smartest thing McArthur did was to insist on Japan keeping Hirohito, after the war.
Yep. MacArthur was a very poor General. But he was the classic right man in the right place to govern Japan. His ego was supremely suited for being a lord dictator to a broken subservient people.
And his masterstroke was keeping Hirohito, but making him admit he was a mere mortal and not a god.
I understand people in Japan today still admire him. They expected utterly brutal treatment in defeat, as they visited on others.