It's not enough that he catch the ball. The NCAA catch rule is complicated and provides that it's a catch only when the runner "Secures control of a live ball in flight before the ball touches the ground, and touches the ground in bounds with any part of his body, and then maintains control of the ball long enough to enable him to perform an act common to the game, i.e., long enough to pitch or hand the ball, advance it, avoid or ward off an opponent, etc."
He failed the underlined portion. The Clemson WR never made a football move. He never sought to advance the ball or avoid or ward off the DB. The DB took it from him as he was falling down. That's not a football move. Hence it was an incomplete pass. Not a fumble. OSU lost the game fair and square, although their coach will tell you and anyone else who will listen otherwise.
He failed the underlined portion. The Clemson WR never made a football move. He never sought to advance the ball or avoid or ward off the DB. The DB took it from him as he was falling down. That's not a football move. Hence it was an incomplete pass. Not a fumble. OSU lost the game fair and square, although their coach will tell you and anyone else who will listen otherwise.