Here is another possibility wrote:
It wasn't by a damned horse either. A two week old pronghorn would have destroyed Secretariat - probably could have run the last quarter backwards and still won.
But that wouldn't have been much an of an achievement for the pronghorn, now would it. Because any pronghorn can do that. No horse could do what Secretariat did, that was why it was such an achievement. Just as no long jumper could do what Beamon could do.
The point is the achievement in question is far and above what any other (of the "breed", so to speak) had ever done. In this case, its arguably above what any others have done since.