Partway through the race, when he saw that Meb Kefelzighi was making a serious move ahead of the pack, he and some other American runners adjusted their strategy, since they figured it was far more important for an American to win -- ANY American -- rather than trying to make a move on their own and risking being overtaken by the large group of elite African runners (mostly Kenyans) who have dominated the race for so many years.
Kefelzighi was out in front of the lead group of elite runners, so Hall and fellow American Nick Arciniaga led the pack with a rather slow pace, allowing Kefelzighi to extend his lead.
Their theory was that once some of the African runners made a move, it would be too late to overcome Kefelzighi's growing lead and as a result, an American runner would win the Boston Marathon for the first time since 1983.
After the race Arciniaga described how it went down:
"I was in the lead pack with all of the other Americans and all of the Africans and about 15k to 20k, Ryan Hall and I were running side by side, in front of the lead pack but not really pushing it, and Ryan just kept turning over to me, talking (to me and saying), ‘Hey don’t push the pace. If [the Africans] want to let [Meb] go, they are going to have work to catch back up to [him]. We are not going to help them out with that at all. If we want an American to win, this is how it’s going to be done.’ "
It worked, with Kefelzighi eventually winning by 11 seconds.
Great job by Kefelzighi, and of course by the rest of the Americans who helped him and turned one of the great individual sporting events into a team win.