I think the author might be misinterpreting The Black Swan Theory when he says this: " . . . Nassim Nicholas Taleb and Benoit Mandelbrot postulate that seemingly very improbable events take place because the probability distribution turns out (mainly in hindsight!) to have "fat tails"--that is, instead of conforming to the "normal" Bell Shape form, the distribution has a shape in which the probability of extreme events is greater than normal."

I think what NNT is trying to say is not that the probability of the tails extreme events is greater than normal but rather that these Black Swan events are rare and we tend not to predict them due to our bell curve obsession. When they do happen however they're game-changers.