He didn't hit the hydrant and the tree head on, he backed into them.
His head probably bounced off the headrest and into the Steering Wheel when the Escalade hit the tree and stopped.
From where the fire hydrant is located on that video, it seems odd he’d still be in reverse at that point. Maybe I’m not seeing it correctly. Anyway, sounds like maybe his injuries weren’t as bad as first reported. That’s good.