Finally when it comes to MacArthur, there is a certain amount of responsibility the US has to face for not relieving him for disobeying orders. They could have done it much earlier.
Stalin could have relieved Zhukov of command any time he wished whether it was necessary or even wise.
Nobody could relieve Halsey of command when he deserved it after Leyte or the typhoons.
The military was not apolitical at the time, nor were its officers apolitical figures. It is in a large part MacArthur's lasting contribution to the US military that they cultivate that completely apolitical air they do now. MacArthur was a viable candidate to depose FDR in the '44 elections and some people argue the US liberated the Philippines to keep him from running. Similarly he was still a viable Presidential candidate during the Korea years, wielding considerable political clout and being possessed of allies in Congress and the press that would have made any attempt to remove him politically impossible. They couldn't relieve MacArthur earlier than that. His war record was superb, his management of the occupation of Japan had been all but divinely inspired in how well it had gone, and his political clout was immense.
MacArthur had to go above and beyond, into the realm of flagrantly and utterly impermissible behavior, to get relieved. Everyone knew it, including him, which is why he did the things he did. He thought he could get away with it.
The alternative is basically President MacArthur and we get him provoking nuclear war with China, so I'm going to have to strongly disagree with your analysis, because that was a very realistic possibility.