One of the main ways Facebook succeeded was that it started at Harvard and expanded to other elite schools, then gradually opened to more people. The platform was rationed such that it was something you just got access to, that the cool kids were already using. I’d argue that social justice organically grew through a similar pathway.

Top schools are full of high class young adults. That includes wealthy kids and lower-income kids who nevertheless have high status in their own communities. Many thousand such people studied social justice in humanities classes in the 90’s. They spread those ideas to their classmates, and after graduating, moved on to lead successful careers in law, education, politics etc. where they spread those ideas to more people until they filtered out to society at large.

The missing link you are asking about between academic papers and mass media articles is that the journalists who wrote the mass media articles studied the academic articles in college. I know this firsthand, I went to college with some of these people.

For me personally, a big part of the appeal of the social justice mindset is that it helps me feel like I’m on the good team while earning gobs of money for doing easy work in the tech industry while a lot of others are working hard and struggling. I imagine it’s similar to the popularity of communism in intellectual circles many decades ago, before that ideology was discredited by practical failures.