1. Looks like he's running sub 7:00 pace
2. He appears to be struggling as hard as one does in a hard tempo or VO2 max repeats, which would mean he could only hold that pace for 2-30min, why would you strain that much doing insane long runs?
3. Too much body fat.
4. Poor form, not taking enough steps for that much distance.
Fossilized deep in the early strata of this thread is a link to an article that mentions he was starting at 190 lbs and planned to drop a couple stones over the first several weeks.