So is the Olympics a new type of porn?

funny you mention this. I was thinking of the same thing during opening ceromonies. Not all of them are gorgeous, but yes most.
This is my explanation. At least for 1st world countries. The people that compete are those that have the money to be able to spend all that time practicing. You normally have to come from money to be able to dedicate your life to your sport. You can't support yourself and kids, etc, if you don't have a job. And if you have a job, you can't spend the proper time practicing at your sport. Coutries like Russia, (at least this was true before) support their athletes financially. Others like ours have rich people/families that support their athletes.
Now I said all this to set the stage, because almost all rich people are beautiful. Rich man has hot wife, and vice versa. After years of breeding, you have attractive children, that are healthy and rich enough to dedicate themselves to a sport. I think its a simple as money attracks beauty, which provides hot offspring.