Diplomatically it was a GREAT move. Problem is that it was a WAR! You don't act diplomatically in a war, you go for the throat! To me Kennedy's finest hour was tax cuts and his support of Civil Rights.
Going for the throat meant mushroom clouds over Miami and Washington.
Kennedy did indeed enact an impressive tax cut. As for Civil Rights, he was too timid to take on the Dixiecrats. The Voting Rights Act, which had languished under him, was actually promoted and passed by LBJ.