The common denominator is the ability of human beings to work with abstract concepts. It's a consequence of a highly developed cerebral cortex.
It comes at the cost of instability. There can be parallels with withdrawal in thinkers and autism, but a very small proportion of autistic people, known as autistic savants have enhanced cognitive ability. The type of autism known as Asperger's Syndrome is particularly associated with savants.
Some of the most influential thinkers in history were bordering on that condition. Einstein is a prime example.
Stephen Hawking did not suffer from autism, but had no choice but to withdraw into the workings of his mind as a result of his motor neuron disease.
The common element is the cerebral cortex, and the use of it, and like any other body part, the more you use it, the more developed it becomes. With the brain, it's the neural pathways that become defined as opposed to muscles. Also in general terms, the body tends to compensate for malfunction of an organ or part of an organ by improved function in other senses. With Hawking, the brain no longer performs the task of controlling a wide range of bodily functions, and consequently abstract thought processes were enhanced. I think that is the key.
Just for laughs: