When Patrick Rodgers missed a birdie chip from the apron behind the 18th green, DeChambeau had plenty of ammunition for all his detractors.
The John Deere Classic has been a launching point for golf careers.
"It means a lot to have Bryson as a victor because we already have a relationship with him", Peterson said.
Daniel Berger had a 63 to match Scott Stallings (64) at 14 under.
Bryson DeChambeau became the latest to make a professional name for himself in the Quad-Cities on Sunday afternoon.
Rodgers, meanwhile, had found trouble off the tee on the 17th and failed to recover as he dropped a shot.
Australia's Cameron Percy continued his hot trot in the tournament, shooting an impressive final round four-under-par 67 to finish tied 12th, five shots off DeChambeau. "Today was a day I had my chances and unfortunately down the stretch I couldn't make any".
"I definitely think they deserve it, you know, with this tournament being, you know, Tournament of the Year last year for the PGA Tour, I think it's great for them to get it", said Tavender Jones. "All in all, if you told me at the start of the day that I'd have the same lead I started with, that's a positive thing".
Spain are the new champions after a narrow 4-3 win over top seeds England in the title decider. Six of those birdie putts came from inside 10 feet.
Langer's closing 73 gave him a 17-under-par total, one behind McCarron after he finished with a 66, set up by him racing to the turn in 31. "This week I haven't driven it that well, but I've kind of kept it in play for the most part and I've made a bunch of putts, which has been the difference", said Berger, one of only two players in the top 10 in the FedEx Cup standings in the field.
Rodgers had to settle for second place on 17 under.
The triumphed with a net 70.5 in an event featuring a group of 42 men and women over the back nine at this week's Open Championship venue.
"I can't control what anyone else does".
"I can't believe this happened", said DeChambeau, overcome with emotion afterward.
Third-placed Johnson, meanwhile, continued his remarkable form in his hometown event, where he finished in the top three six times over seven years from 2009 to 2015, including a win in 2012. But he followed an eagle on the 14th hole with a double bogey on No. 15.
Miguel Angel Jimenez was fourth on 16-under while Colin Montgomerie closed with a 68 to finish joint-sixth on 11-under.
"It's pretty special to have my first win to be here, and it's many thanks to him".