Of course, this really shouldn't a surprise. Even as of 9pm (when I heard all the brackets were busted), 24 games had already been played. Though the tournament was only in its second day, and still the in first round, the odds of having a perfect bracket stood at around 1 in 33 million...assuming the guesser selected randomly. While an educated guess likely gave slightly better odds, the upsets completely undid conventional wisdom. In other words, it's amazing all the perfect brackets aren't dead even earlier.
And yet, every year, many believe they have it all figured out. They've finally discovered the one in a quadrillionth combination that will guarantee them a once in history achievement of figuring it all out. And every year, everyone fails. So why? It probably all comes back to the old adage that humans, for as much as we like to complain, are much more inclined to believe something good "might" happen than something bad "might occur". Suggest that there "might" be cake offered at the party and everyone thinks its a given. Suggest that you "might" get pulled over for speeding, and you'll likely think "eh, that never happens to me"! It's a strategy which has been generally beneficial to the human race...allowing us to say "why not?" instead of "why?"..but it sure makes everyone look silly come bracket season.