You cant land with your full bodyweight on a QB and he did.
When tackling a passer who is in a defenseless posture (e.g., during or just after throwing a pass), a defensive player must not unnecessarily or violently throw him down or land on top of him with all or most of the defender’s weight. Instead, the defensive player must strive to wrap up the passer with the defensive player’s arms and not land on the passer with all or most of his body weight.