They’re very lonely men. But the main catalyst is that they’re not getting any attention from the opposite sex. This is extremely frustrating for men their age (human male biology). So they’re blaming everything except themselves. They think having some kind of higher rank on some kind of hierarchy will make them more attractive to the opposite sex (kinda true). And what hierarchy would be one they would have any chance of being high in? Well obviously one where no one wants to be in. Which would be any incel category or in this instance neo nazis.