Think of the days before idle animation, where our platforming heroes did absolutely nothing unless we told them to via button presses. Set your controller down and Mario would just stand there not moving a pixel as a Koopa Troopa walks towards him with intent to kill. We were playing as Mario, he did nothing without us, but our view of the action was not his own. Somehow we're playing Mario out of body, watching our adventure from the sideline and telling ourselves how to proceed with a vantage of the larger picture. Looking at Mario's blank, dead, expressionless eye sockets gives a clue of how this can be. The player is actually acting as Mario's disembodied eyes floating off screen, somehow still telepathically telling him how to move and react on his mission to rescue the Princess.
IT'S ALL SO OBVIOUS!!!