This is a really key point. While teaching is certainly a separate skill from doing, there is also the fact that the top performers in any given field may have never truly been novices in the way most beginners are. Think of Andy Bolton deadlifting 500 pounds on his first ever attempt. What is he supposed to tell someone about how to do it? He never struggled, never had anything to learn. It's why Michael Jordan and Kobe Bryant were such terrible teammates. They just got frustrated that the game didn't come as easy to other players as it did to them and yelled at them for being shitty.