As 1975 grew closer the Watchtower was already back pedaling a bit about that date being the end. For a while not much was said about it, some people still believed it was going to happen any time, others did not, mostly people didn't talk about it. By the time the Watchtower did talk about it, they basically tried to shift blame, acting as if some people "went ahead of the things written" when the reality was that they did everything they could to make people believe that the world was ending while not actually saying so in so many words.
I am sure some left because of it, but most people accepted the half hearted explanation, because to do otherwise would mean that they would have to admit they were wrong to put their trust in the Watchtower and also it meant would have to do something about it, something most people were not willing to do. It was just easier to accept the lane excuse and go on with their way of life. I know because I was one of those people. Like many, I had invested years of my life in the religion and wasn't ready to face the possibility that it was all just a lie.