Could an unlucky un-contained engine disc failure explain this?
Looking at the damage to the main spar of the qantas a380, it seems possible that if a similar failure (trent 900) occurred through a smaller spar (assume 777 is smaller than a380) and the trajectory was unfortunate and it took out say the top half if the spar (you might recall the a380 went through middle) then total and unsurvivable structural failure of the wing is plausible, no?