With respect to the 890 rider, I think a strong case could be made for multiple types of fatigue setting in. Physical, brain fade, and probably nourishment and dehydration.
They set out with the sun just up and with very long low shadows, so (hopefully) had an early breakfast (6-7am?), met to talk for a bit, then rode 40+ minutes on the roads to get to the base point. The 890 and 1290 were doing everything asked off-road and other than being faster than probably prudent he did fine and showed some experience in his choice of lines.
BUT - His choices degraded at about 7:45 when he could be heard breathing harder than he had been.
The sun shadows say it is at least mid/late morning by the time he gets to the first time the bike is seen on its' side. HeliMark's old ride goes by at 10:20 with the bike laying down and the rate of dropping it gets worse after that. The rider's speed is also faster with his faster breathing and the dash becomes visible more often as he probably is on the seat more often, implying degrading judgement and being worn out while he just tries to push through. While the other guy has a camelback, they are not seen stopping by this point for a power bar or water when they've probably been riding for at least 4 hours since a real meal, and physically exerting themselves for at least 3 hours. The only problem I see with the 890 is that he had to contend with the heavier weight for hours.
How many of us have done this? I sure have. Something to remember.