https://www.irunfar.com/twenty-one-runners-die-during-100-kilometer-ultramarathon-in-china?fbclid=IwAR2HZCLCzA7PhqZ-d2p_aU1bWqG5CECD5Irsfllyi7anz2pTUaaHylOQ2po

Reading around I see some questioning how this could happen, but I get it.  Years ago 7 miles into a marathon I had a good lead in 1st and was getting warm so I threw the shirt under my race jersey to a friend at the 7 mile mark.  At around mile 13 a cold front hit WAY harder than any forecast....30mph wind, freezing rain/sleet.  By mile 17 when my wife tried to hand me a gel it slipped right through my hand because I couldn't hold it, my hands were froze.  At mile 23 2nd place caught me, being young and stupid I wouldn't quit because I was on the podium.  I finished, delirious, and spent the next three hours on a hotel couch under a pile of blankets with hot soup being force-fed to my by my wife who is a nurse.  She considered whether I needed to go to the hospital, worst hypothermia I've ever had.

Now add altitude, probably 60mph winds instead of 30, terrain, and zero help available even if you want to stop...I can see how this could happen.  I've been in bad conditions in the mountains with full gear to the point we were concerned and we had fully adequate gear.  Can't imagine being in that perfect storm only equipped for a normal race.