Doesn't matter how much lift or how big his tires are if they're not touching the ground. He's got it where it's balancing between two tires on opposite sides. That's the problem with open-differentials. When one side is in the air all the power goes to that side.
That's what I was thinking. Also Land Rovers are known for having a crapload of suspension travel.
A few years ago at Wellsville, OH I pulled out a stuck Rubicon with the Ranger I had at the time (no offense). Dude simply high-centered it, admittedly not an easy thing to do with a Wrangler, and all the lockers in the world aren't going to help you when the tires aren't touching the ground.