[sumitviii]

>while being almost incapable of any physicality

Only for the later (even if major) part of his life. One could argue that the physicality he was capable of in the earlier stage of his life helped him gain a solid understanding of physics on our level.

But there is a better argument to be made: Modern Physics is an entirely different beast. To understand the underlying reality you have to be, in one sense of the word, be detached from the reality. And being paralyzed can be said to be one of the many things that let him have experiences unlike that of any almost any other human being. His earlier life let him have a solid footing on the dynamics of our level, and his later life allowed him to depart from it, in a direction in which he was propelled by his intellect.

I would argue that if Stephen Hawking was a sports instructor (or even a programmer for a sport software), his lack of physicality would have worked against him. But if you showed me someone with a severe physical disability who writes great code for sport software, I would revert to my first argument.

(I just explain what's in front of me! :P)