It was his first stop so me you could say the nut might have been cross threaded when the car was put together in the garage before the race. Unlikely I know as there is (normally) very little pressure on the mechanics at that time . But the level these guys are at I would think that unlikely.
Were his wheels off on the grid before the start , or just in blankets ?
The guns don't appear to be soft start, pretty much all or nothing . Either way a pretty crap way of ending your race for (arguably) the best team in the world.