A partial answer,, not the only answer by any means, but I am convinced that instincts for the game of baseball accounts for most of such things. A person either has the instincts, ie., feel for the game of baseball or he does not. Not coachable for the most part. They got as far as they have due to reasons other than basic instincts for baseball. Athletic ability, maybe, or who knows what breaks they got along the way, many of such breaks not earned. This is where superior scouts, ones that go way beyond the stats, etc come in to play. Yes, the human factor in scouting. IMO nothing cheapens the game of baseball as much as players who do not exhibit excellent instincts for the game.