This play had to be something we gave away in film or something. The DB completely ignores Morgan, has his hips open to DPE at the snap, and makes an incredible break on the ball.
Lee is tardy getting the ball to Pierson-El. He needs to have that ball out of his hands as quickly as the Arkansas State QB threw their bubble screens, but even with Lee's tardiness it takes a single-minded focus by the DB on Pierson-El to make that pick.
Of all the improbable plays in that game, this is probably the most improbable. It's a 10-14 point swing, and literally the difference in the game.
If Lee sees the DB breaking for DPE, he could pump-fake and throw a walk-in TD to Morgan, who is left alone & uncovered ten yards from the end zone.