I think I have the answer.
First, I have argued, as have others, that the sexual freedom of the baby boom was the result of demographics. I wrote about it in Baby Boom II. When an age cohort has far more members than the cohort ahead of it, we get an effective surplus of women. Women historically tend to mate with men a few years older than they. So the large cohort 1946-50 had far more women than the small cohort ahead of it 1940-45. Women under these circumstances seemed to be very generous with sex. I remember it with ecstasy.
The sexual freedom seemed to last for fifteen years until about 1980 when it became less casual and less available.
This leads to my second and main point. From personal experience, what I remember happening is that the alpha males who had gathered and enjoyed many women began to squabble among themselves. I can remember many communities falling apart in battles over women. Women became angry with men for taking advantage of them and men seemed to fight each other over the issue of sexual license. Me included.
I record this for the people who will some day seriously look at the hippy period.