The 20- and 30-somethings of the 1950s, remember, were the Americans who had survived both a Great Depression and World War II, back to back catastrophes that touched almost every family. So that generation (also sometimes referred to as "The Greatest Generation") felt the 50s were a time to settle down, start families, buy a home and enjoy what life had left to offer. It was in this national mood that conformity took root.
It was accelerated and intensified by the Cold War, as the possibility of a nuclear war or at least World War III with the Soviet Union seemed a real threat. The Second Red Scare (McCarthyism) spread fear as Americans were investigated and questioned and a sense of hyper-patriotism developed that also was conformist in nature. The playwright Arthur Miller tried to point out what a witch hunt McCarthyism had become in his 1953 play The Crucible.
Sloan Wilson published The Man in the Grey Flannel Suit in 1955, highlighting and criticizing how Americans had come to define happiness as working 9 to 5 jobs in an office or factory somewhere, and questioned whether or not there was more to life than that.