I think EY is pointing to the case of somebody winning the lottery twice in a lifetime, which people would think is incredibly weird, despite it being very normal - see http://www.amazon.com/Understanding-Probability-Chance-Rules-Everyday/dp/0521833299. I suspect that the "looks weird" due to having the wrong model is more common than "looks weird" due to being an outlier.

Indeed. The impression I get is that in calling Objectivism "the unlikeliest cult in the world", the intent of "unlikeliest" isn't as a further insult to Objectivism. Rather, it's to show that the author is discussing something exceptional, and therefore interesting.

I think the point is that if something happens, it has probability 1 of having happened, so it doesn't make sense to call it "unlikely." A perfect model could have predicted it with probability 1. If you failed to predict it, it's because your model was imperfect.

I think, however, that plenty of reasonable models of group interactions given our current knowledge would have failed to predict the rise of Objectivism.