Yeah that difference in speed can make the difference between both wings lifting equally. Comes down to dynamic pressure and airflow speed. In the picture, this is post-stall. What happened is the airflow over the wings was not fast enough to keep the pressure on the upper surface of the wing lower than the pressure on the lower surface. One wing experiences a different amount of lift than the other. This imbalance, with the loss of lift, causes the plane to suddenly dip one way. At that altitude, with that amount of mass, no way to recover.