I wonder if the enormous amount of speculation can be reduced to this. A reliable source stated he has direct visual evidence from a pilot who witnessed the whole event. That was the 777 landed very hard and bounced. The crew went around from the bounce, retracted the landing gear but instead of climbing away the aircraft maintained semi-level flight at about 100 feet then simply sank into the deck. This suggests that there was a failure to apply sufficient thrust to climb normally after the go-around. Exactly why the captain failed to ensure sufficient thrust was applied for the go-around is unknown as yet. But chances are there was a f**k up in the cockpit along the way.