When I read the title, I had been expecting some sort of elaborate conspiracy theory disproving the existence of the Buddha. But instead I got a pleasant story!
I really quite liked the story, and it saddens me to see how many people have given you a hard time about it, when the meaning of it seems blatantly obvious to me.
The junior monk, in his grief, had doubt in the teaching of the Buddha (the dharma), because he could not immediately see the good results of his master's positive Karma. This is why he says that the "Buddha is fake," as in the Buddha's teachings were inaccurate since (the way he saw it) the law of Karma did not apply here. However, he comes to realize the fruit of the Karma, although it was not immediate, and loses all his doubts. What's so difficult about that? It's a simple teaching of Karma, nothing more, nothing less.