The Japanese could have dealt with Guadalcanal OR with New Guinea, where excellent Australians and the American 32nd Division (Wisconsin farm boys, an activated Guard Division, and the first American Army Division in combat, I believe, and definitely my people!) but not BOTH AT ONCE. The Japanese figured New Guinea as the more important battle, then decided, no, Guadalcanal was more important, then they changed their minds again, and then again one last time. Played hell with logistics, timing, and morale. The Battle of the Bismark Sea put an end to this period, to my mind.(Bismark Sea is worth a Foxhole, an important turning point, and real tough on a lot of Japanese).
MacArthur was the fellow who persuaded the Joint Chiefs to invade Guadalcanal, because MacArthur could see that the Japanese were going to win in New Guinea otherwise, and Australia and New Zealand would be lost, and access to the Indian Ocean. MacArthur was one smart cookie. Maybe even as smart as he thought he was! And boy, was that smart!
On the other hand lots of "Old Breed" Marines had no use for MacArthur, since he had made the Marines pull the Army's fat out of the fire. But that "Old Breed" resentment was gone by Okinawa, an old Marine who was there told me, and the Army and the Corps were like brothers.