Last but not least: he lacks the ability to recognize the advantages (if only for implementing his own goals) of perspective-taking, compromise, being physically presentable (ie dressed decently, hair groomed, body clean), the slightest bit amicable/sociable...
....and not doing things that are socially repugnant. Such as threatening suicide when women won't date him (numerous independent accounts of such behavior, mostly with women who were very young), picking his toe cheese and eating it on a stage (there is video proof of this), repeatedly expressing extreme views around sex trafficking and pedophilia (and then when called out on it, nothing but petulance), hosting semi-clothed cuddle sessions on bare mattresses in his office at a university campus office building, and so on.
He's so blind that he can't even see that his continued presence at the FSF in a leadership role has cost the FSF the vast majority of its working relationships with other organizations, free software or corporate. The FSF board is right there next to him; they're so devoted to him that even when almost the entire open source community says "if you won't fire Stallman, we're done working with you", they won't get rid of him.
Stallman and the FSF had been increasingly irrelevant in the thirty years proceeding the whole pedo/trafficking emails and sexual harassment blow-up. Given the reaction from both, they've since become even more irrelevant.