He did not have time to set up, plant and launch... which is why you never see qbs at this level scramble out of the pocket and do that. The hit was exquisite and should have resulted in an interception. The QB should thank whoever the defender was for not ending his career right there. If I had to have someone smoke me like that with a running start, I'd want the hit right on the thigh like that from straight on. Femur is the biggest bone in the body and the biomechanics of a hit like that lift your planted foot off the ground which is exactly what happened.

Lower leg shots are cheap shots imo. I hate when a db goes at a tight end at the knee and below. QBs need to be protected from those, but I can't count how many times a shot to the thigh was called roughing the passer. It's obvious in real time. I don't know why refs can't figure it out.