So the timing coincided with the explosion of Silicon Valley; combine with their genuine presence there to some degree, and hey presto...

I'd also suggest that Asperger's is inherently flattering to some degree: it inherently implies you're smart, and capable in some field. ('Yes, I can't understand people but that's not my fault, I have Asperger's, which also means I'm smarter than you.')

Schizoid on the other hand, besides sounding like 'schizophrenia' (zero positive connotations), looks bad even when you read the entire Wikipedia entry: almost like a synonym for sociopath/psychopath. (Funny thing, BBC's new Sherlock series has Sherlock as a diagnosed sociopath, so even that diagnosis may yet be redeemed.) It's not clear why anyone would want to claim a self-diagnosis of that, since little about it is 'egosyntonic', as the psychiatrists say.