The commentators started this by saying the elbow was down , so it was a catch.
If you watch the whole play, Chambers was bobbling the ball after he first caught it, then secured it, but never made a move after that because he was already falling toward the ground. Champ also had his hands on the ball at that point. The camera angle did not show clearly who had the better grip on it, but Chambers never made a football move after securing the ball.
The REF on that side of the field clearly thought that Chambers did not have full possession when he hit the ground.
Also I thought the rule was that the ground Can cause an incompletion and that a reciever MUST make a football related move after securing the ball and not lose control of the ball THROUGH his contact with the ground. At best the pass might have been called incomplete if a review had been possible.
Also when Chambers caught his LAST TD over Paymah, it did not look like he ever had full control of the ball. It was sliding down his body on the left side and then it bounced over to his right hand. He sure SPIKED it fast if that was a catch! Not sure since they only showed a quick replay once and SD hustled on the field and put the kick up as fast as they could.