He has dreams. He believes that he has a god-given talent. He has delusions of grandeur. He expected instant results. However, it is obvious that he had not the skills, nor the talent for it.
Telling him the brutal truth will only enrage him and shatter his idealism. The others have been tempted as well but they had decided not to play god.
Not telling him will see him follow the course and probably learn the hard way. Experience teaches. It is probably for the best. Pain and experience.