Seems strange to me to feel imposter syndrome for not matching up to an elite talent… did you feel prior to this that you were the best in the world at programming, and now realize you aren’t? Is everyone who isn’t the very top of the top an imposter?
Maybe he is smart and could do it but he is just very lazy and prefers to lie in bad playing games. That would cause him to feel that way when he realises that he could do more ;)