Jetdoc,
You say you"cant imagine anything going on prior to touchdown" before landing .I cant believe you fly.I`m talking about all the check list items ,many of which are done without a physical cross check by the other pilot.
Ive seen enough errors and ommissions to know they can happen with familiarity, tiredness or stress or even lack of knowledge* .We know for a fact that one such error took place the during the close down checks* .( no criticism implied here)
I dont know the standard 777 check lists and SOP, but sure as hell some change which occurred took place on this flight ,either in technical or flight conditions or in standard actions which triggered the whole sequence of double failure .
Think of ALL the things that happened in the whole flight and before. We can only pick them out a few at a time, there must be thousands.