The storm must have been crazy. I know weather can change very quickly in the mountains and have been out in it when it goes from 80F and sunny to 40F and raining. Sounds like many got lost and visibility was bad. Ive had low visibility on well marked trails where I could only see a few yards in front of me. I can't imagine if it was off trail or poorly marked.
People will point to hard rock or the barkley as examples where extreme weather is common, but also remember that both these events have qualifying requirements and reputations that would ensure most know what they are getting into. Perhaps this race was somewhere that is normally warmer and the forecast was for it to stay warmer. I dont know, but im sure if the participants had expected bad weather they would have prepared for it.