Interesting article. It really seems to check all the boxes when it comes to era and extremist lefties in general.
The economic link seems particularly interesting. The USA is, to the rest of the world, known very well as exploitative of its own workers, to many of its residents. Low wage, shitty work conditions, lack of accessible health care and so on. It's basically the only first world country in the world being as asocial as it is when it comes to the lower income bracket. Mind you, we have tons of low wage jobs in Germany too, but you can't be fired easily, nor will you find a lack of health care (our health care has some problems, but not being able to afford something isn't one of them).
If you then add a minority person that is, to a degree, sensitive about their minority status, and this lack of faith in oneself due to low economic status and no improvement in sight, the "great uncertainty about personal significance" as outlined in the article, putting your values of identity into some group you bond over the issues you have with, instead of the self that is disliked, makes complete sense.
Seems to me like the entire "group narcissism" stems from a very child-like and innocent emotion of wanting to belong and being sad and mad of being denied.
It's the whole "let's bond over us being hurt by not belonging and act like we never liked them anyways" turned up to 11 and from adults. Extremely unreflected behavior.