Two choices as I see it:
-lady luck was in the driving seat.ie.they did have catstrophic power loss and they did just have enough inertia to clear that fence(highAoA supports this but large bank angles wouldnt) OR
-the pilot was in the driving seat-it was all by design-partial or significant power loss-(birds..surge/stall)-the highAoA to stall it onto the grass is all intentional-bank angle on app may have been height-loss maneuver-let the gear take it and plough to an early stop in the grass.
Of course,the other option is a delayed or "sloppy" response to eng fail on short final(explains bank,explains undershoot).
In fact the only thing anyone can say right now is that the Boeing 777 is an incredibly well-built plane.