Hahahaha this is hilarious. I think you do have a point...many great pianists probably became famous PARTLY for their beauty (Glenn Gould, Paderewski, listisa, on and on). I mean, classical music performance is a type of show biz, after all isn't it?
I personally think Martha became famous because she won the international Chopin competition at a VERY young age, and because her technique was top notch (and still is), and because she pretty much played (and still plays) everything a tad over tempo (ahem).
Also I think the magnetism we find that draws us to certain performers also has to do with their personality...when have you found a famous pianist that wasn't quirky in some way? (I don't count listisa, because I don't like her.) Martha is particularly interesting because she always plays with a certain objectivity ... She always seems kind of aloof and distant but some of her recordings are simply amazing (especially Prokofiev, even though she plays like twice the intended tempo, but prokofiev is my favorite composer, so meh)
Okayyy, I wrote a lot mor than I thought I would! Hope my insight is helpful, or interesting at least!