John F. Kennedy's acceptance by the public had much to do with two things:

1)   WWII erased a great deal of America's bigotry toward Catholics, because during the war protestants served alongside Catholics and saw first hand that they weren't slaves of Rome.   Before then, much of America was isolated into pockets of parochial believers, and so had relatively little contact with those of other sects.

2)   JFK really did have unusual charisma, and people tend to make allowances for Alphas.