Not to give that other ridiculous thread any more credence, here is why Meb Keflezighi won the 2014 Boston Marathon:
1. Meb is in the shape of his life. He ran a big PB, and one of the faster winning times in Boston history.
2. He ran away early, and only Boit with him, both of whom Americans. The other elite runners did not see them as a threat. When Boit had to fall back, that initial assessment seemed valid.
3. The two top favourites, Kimetto and Desisa, had a bad day. On paper, that still left faster runners than Meb, but the fact that neither Kimetto nor Desisa seemed to show an interest in closing the gap signaled to the others that they should not do so either. Who would want to run away from Kimetto? Certainly not Chepkwony, his training partner.
4. When Chebet and Chepkwony finally dropped Kimetto, it was too late to catch Meb. They closed fast and gained fast but they (just) ran out of miles.
Taken together, a very rare set of circumstances, but a not at all unbelievable turn of events. It also just goes to show that you cannot simply multiply the probabilities of unlikely events based on theoretical PBs, treat them as uncorrelated, and derive a joint probability of < 0.005% of Meb winning, as the Brojos did in their preview. In a race with heavy favourites and no pace makers, it does not take that much to create an upset. Meb clearly saw his best chance in breaking early, risked all, and won. Well played!