Here is supposedly with happened. If you watch the NBC video you can see them coming of the turn right next to each other.
But something else probabley happened in the middle of the race where they stepped on each other or bumped or something etc.
http://www.madote.com/2011/03/eritrean-and-ethiopian-athletes-fight.html
"During the 2011 IAAF World Cross Country Championships in Punta Umbria, Spain, Eritrean athlete Samuel Tsegay, and his Ethiopian counterpart Abera Kuma, were involved in a fight during the final hundred meters of the race.
According to Spanish news agencies, Tsegay and Kuma first started displaying aggressive behavior towards one another around 11,900 meters of the race. The tipping point that ignited the brawl didn't start till the final home stretch, when Kuma of Ethiopia deliberately started elbowing Tsegay and stepping on his shoes from behind, in order to prevent the Eritrean from sprinting to his full capacity. It was at this point when both competitors tripped and fell to the ground, and a infuriated Tesgay rising up to grab Kuma by his right leg and deliver blows to his adversary.
Although both competitors crossed the finish line, they were nevertheless disqualified. This incident has quickly gained notoriety throughout Europe and has prompted an investigation from IAAF officials."