ESPN's Nick Friedell broke down the situation on the Brian Windhorst and the Hoop Collective podcast.
"Chris Bosh, according to more than one person in the organization, said that, 'I'm coming to play for the Bulls.' Straight up," Friedell said (h/t Dan Feldman of NBC Sports). "He said: 'I'm coming to play for the Bulls. This is where I'm going to be.'"
He noted both former players and team personnel thought Bosh was definitely signing with the team.
"As far as the Bulls were concerned, they felt like they had a commitment," Friedell added.
The Bulls' strategy at the time was to land Bosh and then try to lure either Wade or James as a second superstar, via Kurt Helin of NBC Sports.
According to Windhorst, the team tried to move Luol Deng once it became clear Wade, James and Bosh were intent on playing together.
Chicago already had a solid young core with Derrick Rose and Joakim Noah, giving the team a chance to contend for a title with any of the free-agent additions. Rose won MVP in 2010-11 while leading the squad to the Eastern Conference Finals.
The Bulls weren't able to get by the Heat, however, a squad that eventually won four straight conference finals and two NBA titles.
History might have been different if free agency went the Bulls' way in 2010, but Windhorst noted a significant problem was that Rose wasn't involved in the recruiting process. Noah played a part, although he didn't have a good relationship with LeBron.
Heat president Pat Riley also helped convince Bosh to join his team after giving the forward one of his championship rings.
Even with what might have been an initial commitment to Chicago, Bosh ended up in Miami and remained there until his retirement.