What was the main social development in the 1950s?
There are, of course, many possible answers to this question. One possible answer is that the main social development during the 1950s was the development of a conformist, materialistic attitude towards life.
The people who were of working age in the 1950s had lived through WWII and in many cases the Great Depression. They wanted to finally have comfortable, stable lives. This led them to focus on work so that they could buy material comfort for themselves and their families. This was the cause of materialism. At the same time, the Cold War and the fear of communism (among other things) led to the idea that there was one right way to do things and that everyone should act in that way. This was a major cause of conformity.
The main social development, then, was the development of a materialistic and conformist society.