One must note that the bloke was essentially saved by an EPIRB, and he was only encouraged to carry the EPIRB at the last minute, when a concerned friend gave him his.
I think "thoughtlessness" describes well, this blokes "mishap" - and thoughtlessness is to blame for many a life lost.
If he was 18, one could say it was teenage thoughtlessness and impulsiveness to blame - but the bloke was in his mid-20's when he set out on the trip, and one is expected to have a modicum of maturity and ability to think things through properly, by then.