Before it had the 2008 games sewn up, China planned to bid on then using a September start date. But this would collide with NFL coverage in the U.S. and thus dampen ratings, as occurred in the 2004 Olympics in Sydney. NBC, which already had TV rights to the 2008 Olympics, urged China to consider moving the date.
So China proposed a mid-August start date in its official bid, and won.
But it turned out that date interfered with the U.S. Open, meaning tennis stars would skip the Olympics, meaning more ratings pain.
China looked at the $894 million in NBC money it had already deposited into one of its banks and decided to accommodate one last change request from NBC, to August 8. Americans looked at the price of gas and the lack of money in their bank accounts and decided to stay home and watch the Olympics rather than go out at night or on vacation. Ratings soared and NBC was very "lucky" The End!