My biggest thing was this.....
If he were passing the ball, it would have had more velocity on it instead of simply falling to the turf. The ball would have gotton past the defender, or hit him in the hands or helmet.
When the ball came out, Leak's arm was moving DOWN, not forward. He was about to tuck the ball and take the sack, and the ball fell out of his hand.
Fumble, right call made.