I think our Kiwi mate Offcut at post #717 is on the money. For those who have flown both the 74 and the 77 it is the most logical answer.
My guess is that a hot and high approach was flown in FLCH. That is the only mode that will get you down in a hurry. If the A/P is then disconnected, the auto throttles will remain in Hold, and not "wake up". If a pilot purely concentrated on the aim point and forgot his scan, speed could easily wash off to the point of stick shaker or beyond. FLCH is a major threat in the 777 if used while hand flying and should never be used during an approach. Our SOPs require FDs off, then one back on to force AT into speed mode.
There may have been speed brakes involved but that does not change the basic scenario...airpseed bleed is corrected by gripping the handles and moving them forward.Noone did that until 1.5 seconds before impact.
So when the PF finally picked up the GS from below he was out of inertia. The fact no-one else in the cockpit was awake at that specific moment is the most interesting conundrum.