There is of course the “other option” that none of you armchair investigators have considered.
Dave accepted a task when the aircraft was almost out of fuel. 3 experienced crew accepted a task with nothing in the tanks?
There is a known problem that the fuel system shows permanent full supply tanks plus a bit in the main, if the sensors were water contaminated. When the fleet were tested LOTS failed.
Care to consider he was looking at 100+kg on the gauges when the engines stopped? Care to consider the unguarded switches got knocked during the recovery ops?
There’s always more to armchair assess