This began in earnest in the late 1960s and early 1970s, during the Vietnam War.
One of the great fears of young men during that time was the lie that unless they had one of any number of deferments, that at any moment they could be “drafted, sent to Vietnam, and diiiieee!”
The truth was anything but that. The vast majority of soldiers wounded and killed in Vietnam belonged to combat branches in “hot” or “medium” combat zones. These were a tiny minority of all soldiers in Vietnam, must less the majority of all US soldiers, who remained in the US or went to Europe.
Even more, any soldier of good character, in a combat unit who wanted to reenlist and stay with his unit, would get that slot, so the unit would get no replacement. It was not uncommon for soldiers to stay on the front for three or four tours.
By the time of Vietnam, the ratio of combat support and combat service support personnel to combat personnel was about 15 to 1.
In any event, back in the US, radical professors would sometimes blackmail their own students with the refrain: “Unless you go to the anti-war demonstration, you will fail this class, lose your deferment, be drafted, and be sent to Vietnam and diiiieee!”
Students, already frightened a lot by the media, and tantalized by the numerous draft deferments offered by congress, were psychologically brow beaten.
The Tet Offensive, in January of 1968, caused by the last ditch effort of the Viet Cong, who had almost been destroyed by the Phoenix Program, effectively wiped them out, but was declared a huge defeat for the US by the media, starting with Walter Cronkite. From that point on, the Democrat party and the media did everything in their power to undermine the war effort.
This gave campus radicals everything they needed to create chaos. So from then, until president Nixon ended the draft in January of 1973, America was effectively in a Civil War between a tiny number of radicals supported by the media and the Democrats, with passive support from terrified young people.
The radicals were already losing, because after the Kent State incident, a lot of the impulse to radicalism ended, because the mood was that the government had finally lost patience with the radicals.
The end of the draft killed the anti-war movement. All that was left were universities filled with a new generation of leftist professors. And there they remained.
The large, peer-pressuring contingent of Baby Boomers just reaching college age at the outset of the Vietnam conflict;
Post-ww2 affluence sending more young people to college AWAY from home, parents and the values they were raised with than ever before;
The completion of the interstate roadways and access to cars and transportation as never before;
The legalization of the Pill and abortion and the launch of Pop Feminism (Ms. Magazine, Bella Abzug, et cetera) during the Vietnam conflict;
An uptick in non-Christians in positions of power actively seeking to water down cultural solidarity;
Ted Kennedy's 1965 immigration bill favoring nonwhite non-Europeans; and
A generalized rage against "the establishment" arising from the Civil Rights movement.
A perfect storm of inducements to youthful gullibility, rage, fear and irresponsibility.