Carolina got screwed on that challenge but you gotta hold onto the ball Cam
Ball moved, wasn't a catch.
It's not relevant whether the ball moved. This wasn't an out of bounds play. It was in the middle of the field. The only thing that matters is whether the ball touches the field sometime before the completion of the play. It didn't, therefore it was a catch.
The only reason it could have stood is they weren't certain whether it touched the ground or not.
BTW, if you're going to the ground, you have to maintain control. Whether you're in bounds or out of bounds has no bearing.
Maintaining control when you're catching the ball in the middle of the field means keeping the ball from touching the ground. That is all there is to it. Therefore it's important to distinguish between in bounds and out of bounds catches. If you're falling/running out of bounds and juggle it, you are not maintaining control. If you're juggling it and still in bounds and the ball never touches the ground, you are maintaining control.
Rule wording:
"If he loses control of the ball, and the ball touches the ground before he regains control, the pass is incomplete. If he regains control prior to the ball touching the ground, the pass is complete."
If a player is laying on his back and the ball falls down to him and he catches it, it's still a catch, even though he didn't even touch (or "control") the ball before he was on the ground. If there's an example of any other play where the player caught it within bounds and it did not hit the ground and they say he didn't control it, please enlighten me. I remember the infamous Calvin Johnson TD but it's a different argument because he slammed the ball to the turf.
Again, the reason this call stood is because they thought it touched the ground at some point - because that's the only way you can lose "control" while still in the field of play. (Unless of course you're not done completing the catch and decide to toss the ball to the referee or the sideline.)