It is very interesting when you explore the neurological mechanics of this. A narcissist is rigid thinking dialed up to 11. It is essential a special and pathological “skill” their brains have learned. They do not have to update their priors or spend metabolic energy on almost anything their life. Their brain figured out the best way to survive and conserve energy was to avoid costly updates to their beliefs. Repeated over years and that system becomes deeply myelinated, a core identity. Unwinding that is a feat. Some people just have a more narrow set of rigid beliefs (e.g. religion, work skills, etc).
Agreed on your neuro take. It would seem that the rigidness is somewhat reinforced by the pervasive mechanism of digital feedback. As we now can see clips of stupid behavior being propagated online as easily as opening our eyes and tap a screen, the rigid behavior of an overt narcissist is now on display as a model for lesser equipped minds to absorb. The narcissist acquires a visually recognizable position of power through their actions, and this makes them highly desirable by those lacking control in their own life. The audience is global... And where the terrain is fertile.. the said audience also votes for their model.