It boggles the mind that this is the same intellect that invented the notion of the Chomsky grammar which is a huge deal in theoretical computer science and an underpinning in how we think about computers, programming languages etc.
I guess there are other cases of this happening - like in A Beautiful Mind - still amazing to ponder though.
Another sad, similar case is that of the brilliant chess grandmaster Bobby Fischer, who became increasingly deranged in his later years.