Society is continually expanding it's notion of minimum acceptability. Standardized testing is a great example. The problem with this approach is that extreme excellence is fundamentally divergent. Revolutionarily smart people don't think the same way but faster. They think differently [1]. Also, excellence in one domain precludes it in others. For instance, you can't be a world class distance-runner and body-builder at the same time. The same holds for mental activities. Effective heuristics in one domain become cognitive biases in another. By expecting and accepting lower performance in general you create room for your comparative advantages to further develop. This can be summarized by the maxim: focus on your strengths. In this case I suspect insurmountable weakness enabled Nash to do exactly that.

1: or "different" if you're too focused to bother with grammar ;)