The chance to bring the Olympics to a continent that had never hosted the Games worked in Rio’s favor. During its presentation, the bid team showed a graphic of the world and marked all the places that have held an Olympics. South America was glaringly bare.

Image People gathering in downtown Chicago reacted to the announcement that the city had been eliminated from contention for the 2016 Olympics. Credit... Tannen Maury/European Pressphoto Agency

“There was absolutely no flaw in the bid,” the I.O.C. president, Jacques Rogge, said.

Chicago officials had worked nearly four years and spent nearly $50 million to bring the Summer Olympics to the United States for the first time since the 1996 Atlanta Games. There were many possible explanations for Chicago’s spectacular failure, but little consensus.

Some pointed to the regional bloc voting in the treacherous first round. Others said some voters, assuming Chicago was a lock to advance because of the presence of Mr. Obama and his wife, Michelle, might have taken their early votes elsewhere. Many also blamed the rocky relationship between the United States Olympic Committee and the I.O.C.

Others said there was no explaining it.

“Everybody was shocked at that result,” said Rene Fasel, an I.O.C. member from Switzerland, regarding Chicago’s first-round ouster. “Everybody expected Chicago and Rio, everybody. It was really strange, and I feel really sorry. If it would have been Chicago and Rio in the end, it would have been much closer.”

Anita DeFrantz, one of two I.O.C. members from the United States, said she could not believe how the vote unfolded, particularly after the Obamas’ visit. “I hate the fact that these elegant people were here and then our country got treated that way,” she said.