context:  This was the first Sunday Night Football game held in MetLife Stadium following a one-season absence. With the loss, the Giants fell to 3-8, and were mathematically eliminated from playoff contention after the Lions defeated the Bears on Thanksgiving four days later. This game, however, is best known for an acrobatic one-handed catch by Odell Beckham Jr. early in the 2nd quarter that would go down as one of the greatest catches in NFL history.  A penalty marker flew as he made the catch - for pass interference on Brandon Carr, who had been covering Beckham on that play.
question: Why did Brandon Carr receive a penalty?
answer: pass interference