I think I noticed something I haven’t heard anyone else mention. If you look closely at the full video, it shows him palming an object from one hand to the other after the hit.
I believe he had a hard metal object inside his fist to increase the force of the hit. I think he might have also hit his temple. Perhaps the metal object was just a roll of dimes, but still could make a big difference.
A fist pack always makes a big difference if you connect.