I have no idea why they promoted it in the first place. Asides from that usual tendency of left-wing movements to start destroying their own society just to spite their "oppressor class", of course.
It's really not that hard to fathom what was going on here, and it's a combination of misplaced idealism, actual bad faith actors who sought to normalize their own perversions, and a timely alignment of technology enabling behavior.
The rise of casual sex culture in the west can pretty easily be traced back to the late 1940s and 1950s. Prior to then, even in the "Swinging 1920s" most folks looked down on casual sex because the actual consequences for women were high risk and permanent (out of wedlock pregnancy) and men who DID get a woman pregnant out of wedlock up until the 1960s was typically forced by society to marry the girl (AKA Shotgun weddings) which meant that there was also some consequence for men.
The attitude towards sex began to change with the
Kinsey Reports, published in 1948 and 1952, which took the sexual attitudes of prisoners, homosexuals, and rapists and pretended they were the normal sexual attitudes of everyday people. The entire thing was arguably a massive scam on Kinsey's part but much of that information didn't come out until the
1990s when people finally got access to his original data. As it was presented to the public at the time these reports were supposedly about "average Americans".
One of the big things the Kinsey Reports did is make it seem like people had more sexual partners than they actually did, which broke down social stigma around having multiple partners.
As an aside, I want you all to again note the years these reports came out:
1948 and
1952. We tend blame the Sexual Revolution on the Baby Boomers, but I would posit that the actual blame lays with the GI Generation that birthed them, you see, the Kinsey Reports greatly impacted HOW the Boomers were raised, and remember none of the Boomers would have been old enough to have read these reports when they came out, since the Baby Boomer generation STARTS in
1946... two-year olds can't read.
Why did the GI Generation believe the Kinsey reports? Why wouldn't they? This was the Generation more than any other that was raised to believe in Experts. They were the ones who grew up in the Great Depression and were bombarded with Experts from the Government "helping" them, and then of course they were the generation that fought WW2 and thus were one of the most militarized generations in American History, and modern warfare is all about control by Experts. Basically you had a generation raised to automatically defer to Expert Opinion on things. Along with the Kinsey report you ALSO had the rise of "
new parenting" methods pushed by Experts like
Dr Spock, and while there was arguably some merit to pushing back against the prior few decades of expert pushed child care advice, between the obvious leftist politics of those involved and human tendency to overcorrect, well, you had the Boomers being raised in a way that was so completely different than prior generations that it created the first major generation gap in American history.
But even with these things you needed a final piece to really overthrow traditional sexual norms. Consequences of casual sex were still sever for women even though society was losing the desire to force men into marriage in the same period due to both government welfare increasing for unwed mothers but also the lowering of social stigma to being a man whore.
That final piece came with the rise of
hormonal birth control in
1960. Note this year, the earliest Boomers would have just been turning 12 years old... just entering puberty, and just as they enter it, they've got a culture that's raised them to be more "in touch" with their emotions, they've been taught that most men and women have more casual sex than they actually did, AND they've been handed a get out of jail free card in the form of birth control... just in time for them to get all hormonal in their teenage years.
Yeah, I know we like to blame the Boomers for everything, but the Boomers were effectively set up by their parents to fail. This is why I have begun to realize that the Generation That Failed was not the Boomers, it was the GI Generation. Yes they fought the Nazis, but it was THEY who put in place the institutions and experts that led to the Sexual Revolution, it was they who placed complete trust in the Experts to guide society and constructed the Institutions that have corrupted society. The Boomers were just the result of their actions, the first victims of our issues, not the progenitors.
Note, we haven't even gotten to the IDEOLOGICAL reasons for the rise of Casual Sex culture. This is also important because even if you had all these other factors in place the inertia of Christian sexual morality likely still would have kept Casual Sex down from cultural force alone. Why do I say this? Because even WITH the ideological rise Christian Sexual Morality was still a major social force into the 2000s impacting how people thought and felt about sex.
But the ideological component cannot be underestimated. The rise of
2nd Wave Feminism, who many like to pretend was about equal pay, but it's not, it was just as toxic as later 3rd wave feminism and one of the core ideas it pushed was that women should be just like men. Going back to the Kinsey reports even in those women tended to have fewer sexual partners then men did, and thus one of the things that 2nd Wave feminists thought was that by having men and women act in the same way sexually, they would create a more equal society. Bear in mind, the period of the 1940s to 1980s was the height of the "blank slate theory" of human development (arguably in part an understandable, if overreaching, reaction against the Nazis eugenics ideology), thus feminism sought to encourage sexual license in women. The negative effects of this eventually led to the split between sex-negative and sex-positive feminism in the 1980s, but in the critical formative years of Baby Boomer education... they were told women and men were fundamentally the same and could behave the same way with no consequences...
All this hit at a time when actual religious faith in the US was at it's weakest. The Mainline Churches had long ago been hollowed out of True Faith due to the Fundamentalist / Modernist conflict back in the early 20th century, with the Modernists driving the Fundamentalists out of the seminaries and universities, and even though most Modernist assumptions about the Bible and Christianity have since been disproven by archeology and good-faith application of historical standards they were still the academically accepted position in the mid-20th century, and that undercut many people's faith. The rise of the Evangelicals did not begin until the late 1970s in what many people don't realize was a hidden Great Awakening that began then and ran through the 1990s as actual Believers left the Mainstream "churches" and became "non-denominational Evangelicals" (and like all the other Great Awakenings before it had major effects on society and politics).
As to the underlying "why" though, most of the Boomers just honestly believed this was what was healthy and normal for human beings, that prior generations were repressed (and oppressed), and that going forward a "free love" utopia awaited people. Again, this is what they were taught. Meanwhile the feminists believed that making women equal to men would improve society, though some also sought to destroy society as it stood and knew such things would encourage that. And finally, Kinsey was a sexual pervert and monster who sought to normalize his own sexual perversions.
