Reported by Jenna Fryer of Yahoo Sports:
Harvick knew he had a problem with his engine and knew his car likely wouldn’t go on the restart. Had he forfeited his position in the running order – a move one would only do as a courtesy to avoid a potential pileup – it’s likely the reigning series champion would have plummeted in the standings and have been eliminated from the Chase
So he was told over his team radio to block as many cars as he could on the restart, an attempt to cling to the best finish possible. Instead, Bayne shot around Harvick’s slowed car then tried to cut back in front of him to get back in line. The in-car camera appears to show Harvick looking constantly in his rearview mirror in an apparent effort to ward off any more cars. The replay, though, seems to indicate he turned right into Bayne’s bumper to spin him and bring out the race-ending caution.