Sham had a lot to do with that.
At the Kentucky Derby, Sham beat the course record, running 1:59 4⁄5 (unfortunately on the same day that Secretariat ran it in 1:59 2/5)
At the Preakness, Sham once again beat the course record... an once again finished just 2/5 of a second behind Secretariat. (It was also the first time that the top 3 in the Preakness were exactly the same as in the Derby.)
In the Belmont, as you can see in the video, Sham ran neck-and-neck with Secretariat, holding a lead at the halfway point, setting the record for the first half on that track... before falling back to last place, having taken on the Legend for 2 1/2 races, and finally giving out. Secretariat trainer Lucien Laurin commented on Sham's performance saying "The horse we had to kill, we did."
i dont know what Belmont you watched..Sham had the lead for about 10 seconds half way thru the first turn...when Anderson called the 6 furlong time, Sham was behind by a good 6-7 lengths...this is probably the greatest single performance by a horse ever run..nobody was gonna beat Secretariat that day... to say it was because of a horse named Sham is just odd.