Likely because Fuentes is the "biggest" of the fringe right wing movements, or was at least for some years. And he is representative of most things wrong with them at that.

Its easy dunking material, and has a legion of easy converts from his ranks of single-brain celled followers who are pissed off and are obviously vulnerable to being convinced with a few appealing words.

Its likely very similar to Brietbart sending Milo to appeal to the Gamergate crowd when that was taking off, the legacy right wing seeing a fresh bunch of angry dissents to recruit from.