I believe that 'it' is not mysterious. It's a combination of stage presence and enjoying being up there. Some people are born to be the center of attention, and some people are not.

It's different from talent. A person can be talented and retiring. Or the opposite. My uncle once told me that he had seen Elvis Presley on stage. His singing never impressed my uncle, but when he saw the man on stage, he WAS impressed. Elvis Presley loved being on stage, and he put on a great act.

That's It.