Johnson was the nearest and went for the ball. He was fouled attempting to gain possession.
The design of the inbound play is a problem, and execution was lacking. AB was sprinting toward the baseline and Johnson was inbounding it from the baseline. There was no room for error. If the pass was deflected or not caught cleanly AB would have a difficult time preventing it from going out of bounds. That is exactly what happened.
Both Johnson and AB with big hustle plays just to get BYU a chance at the free throw.