I believe it's ingrained into racers that they are not to "throw a race" for any reason - it's part of their training and code of ethics - all their focus, all their awareness, is on the finish line and nothing else. Also, Meb and Stefano were racing each other more than anyone else at the end, and were trying for all they were worth to beat each other, and so probably could not consider him even if they wanted to. I think giving him the duplicate gold would have been the right thing to do. But had I been either of the contenders (which I will never be in a million lifetimes), I would have given the race to de Lima.