(Ok, to clarify re: SP musicians, I don’t remember saying anything about a trend (could have, though) although there are plenty.  Music is one of those things that draws people in irregardless of type, and there are plenty of musicians of all types who achieve a professional standard.)

Re: the rest of your comment, I guess I do find people being innately good at things less interesting, at least from a typing perspective?  I mean, I can easily find you a couple hundred ES actors or athletes, but it’s hard to pin down exactly what draws them in, and it would get a little boring watching and posting the same types doing the same things (Variety!  Spice of life!).  I would say generally, some combo of initial ease, having encouragement and resources, and having the mental strength (or desperation!) to prevail through the hard parts. 

Also, if you wanted to conclusively know what specific physical/brain things are making a type good at a specific task or activity, you’d probably want to have some scanning equipment.  I’m assuming that an activity that draws a lot of the same type also caters physiologically to the way that type’s brain/body works.  I can only really speculate about environmental factors (culture, upbringing, etc), which tend to be a little different for each person.

Likewise, it is more interesting for me to type the people in unexpected places, because if they’re the only one of their type in a field, you can pretty much pin their reasons for being where they are on environment.  The ones in similarly unusual occupations have often been influenced, encouraged and promoted by the the same types of people.