How can bobby fischer's cognition and intelligence be so high if he suffered from schizophrenia?

@30
 "And yes Fischer was a schizoid and intelligent. "
++ No to schizo, yes to intelligent.

@32
Which psychiatrist? Source?
Psychiatrist Magnús Skúlason discussed with Fischer in Iceland and stated:
"He definitely was not schizophrenic".

@34
"he had issues though for sure"
++ Yes
https://psmag.com/social-justice/a-psychological-autopsy-of-bobby-fischer-25959 

I have hallucinatory problems, it makes playing chess very difficult as the board will warp and I'll see pieces or ideas that just plain aren't there and are outright impossible. I'll play solid one game, then find everything collapsing another simply because my brain decided to sleep in and I'm stuck trying to fight through brain fog and constant confusion and paranoia. Doesn't mean all schizophrenics would be totally impaired, but often if they have talent it manifests in bizarre ways in whatever field of interest they have. Who was that programmer... Terry Davis, I think. Brilliant, but so enraptured by his inner world that nothing he made could obtain relevance on its own; instead made famous by his antics. Also doesn't mean all schizophrenics have a high IQ. The two aren't always correlated.