I've always wondered what's specifically going on their minds when that happens. I remember getting into shooters and pretty much immediately understanding the two separate axes in Duke Nukem 3D at like age 7-8 (yeah I played violent games when I was young my parents only restricted movies). Maybe that's why? My brain was just better able to learn at that age? Or is it that I am autistic? Is neurology a factor?
EDIT: Just realized, even younger, I played and beat Star Fox SNES, which only had 1 axis, where aiming and moving were bound together. Maybe it was the baby step of playing a simpler 3D shooter game.