It was the hard-charging mayor, Rahm Emanuel (photo above with President Obama) , who lured the draft. As far back as 2012, Emanuel had suggested Chicago as a Super Bowl host to NFL commissioner Roger Goodell, but he set his sights on the draft after it was hemmed in by scheduling and space issues at Radio City Music Hall, which had hosted the event the past nine years. Chicago, though, was no lock, with Goodell besieged by calls from civic leaders in Boston and Los Angeles, as well as Cleveland, Houston, New Orleans, Philly, Pittsburgh, Orlando, Fla., and Green Bay, Wis. The Dallas Cowboys also offered their stadium in Arlington, Tex., as a site.

http://www.nytimes.com/2015/04/29/sports/football/persistent-mayor-gets-his-pick-nfl-draft-comes-to-chicago.html?ref=sports