Why Dave went against his own judgement once airborne is anyones guess. RIP.
DO, as much as it pains me to say it I think the fact the GoPro was turned on right before starting their descent towards Ben More probably says it all. I suspect they found the conditions at 6000' better than expected and decided to get some nice footage of the summit, the sort of thing I'm sure we've all done at some stage.
Their but for the grace of god.....