So let’s take apart the far-right claims:
First, psychologically speaking: why do the reactionary conspiracy theorists even bother? This is a straightforward matter. If you’re misguided enough to play identity politics, whether on the left or the right, then you require a victim (in the right-wing case, European culture or some variant) and a perpetrator (Jews). Otherwise you can’t play the game (a YouTube video I made explicating the rules can be found here). Once you determine to play, however, you benefit in a number of ways. You can claim responsibility for the accomplishments of your group you feel racially/ethnically akin to without actually having to accomplish anything yourself. That’s convenient. You can identify with the hypothetical victimization of that group and feel sorry for yourself and pleased at your compassion simultaneously. Another unearned victory. You simplify your world radically, as well. All the problems you face now have a cause, and a single one, so you can dispense with the unpleasant difficulty of thinking things through in detail. Bonus. Furthermore, and most reprehensibly: you now have someone to hate (and, what’s worse, with a good conscience) so your unrecognized resentment and cowardly and incompetent failure to deal with the world forthrightly can find a target, and you can feel morally superior in your consequent persecution (see Germany, Nazi for further evidence and information).