If I remember correctly he had unhealthy levels of arsenic in his system due to copper mining and production, which didn't help his general heath. On top of that a REALLY hard life had taken its toll on his joints, especially taken together with a few old war injuries.(arrow wounds I think)
A trip over the Alps was at the best dangerous for a man in peak condition, let alone a 30 something oldtimer like himself. (30 was old in those days apparently!)
Although he perished I belive he was very well equipped - food, hunting equipment, warm clothing etc.
Quite amazing.