Truman was unpopular because he had just fired Gen. Douglas MacArthur from his Korean command. Ironic. Truman was attempting to chip away at MacArthur’s credibility so he wouldn’t be a threat in the ‘52 race
and instead, it ruined his own chances at reelection.
MacArthur was fired, in part, because the top brass wanted a Europe-first policy. An all-out effort in Korea would divert resources away from NATO.