Ableism? The fact that Vox is so NPD coded, but everyone immediately assigned him BPD instead, because they saw him "obsessing" over Alastor, and we all know how much BPD is just associated with "unhealthy obsession" and other "romantic" aspects, while NPD is "unacceptable and evil and our favorite character would never!"
While PDs in one cluster can be similar, it is the core that can differ them. And the core of Vox is that he needs positive attention. He needs to feel better than and above others, he needs praise and admiration and control. He is generally composed and professional, he knows how to twist the news in his favor in order to look like he's in the right.
It is just Alastor, his chosen person, that makes him lose his cool. Because Vox opened up to him, he trusted him, let his guard down around him and expressed genuine admiration (which is an extremely vulnerable thing for pwNPD). And then... Alastor just laughs in his face, steps on his heart, tears his trust apart? The narcissistic crash and the narcissistic rage is nothing you can imagine after that.
Vox is not in a good environment. He is not in therapy or surrounded by emotionally available people. Of course he doesn't move on. He makes it his goal, his dream to make Alastor pay for humiliating him, and the fact that Vox has a high status in Pride Ring just feeds into the dream. His chosen person rejected him and now he needs to show Alastor that he is smarter, he is stronger, he is better. Make Alastor feel the same humiliation and despair he felt... Even if it means fucking killing himself and everyone, apparently.
Yes, you can see Vox as a borderline, but like, c'mon now... Hear me out.