"This is not the Bob I worked with," said Brown University (search) professor Leon Cooper, who with Schrieffer and John Bardeen was awarded the Nobel in physics in 1972. "This is not the Bob that I knew."
Based on what I've read, it sounds like he had some kind of psychiatric or medical issue at an advanced age that changed his personality, perhaps Alzheimer's. People rarely change personality that much for non-medical reasons.
I don't have enough evidence to make a strong case, but if my hypothesis is valid, it seems unfair to sum up his entire life as a "zero".
It is the individual who is not interested in his fellow men who has the greatest difficulties in life and provides the greatest injury to others. It is from among such individuals that all human failures spring.
Dale Carnegie, How to Win Friends and Influence People