"What did they do wrong? What could they have done differently to improve their odds of survival?"

Good questions. I and my colleagues have critiqued a number of incidents, some which ended successfully and others in fatalities and trends emerge:
1) generally bad situations develop gradually, typically as the result of bad decisions -

"Should we cancel the trip; heavy snow is forecast" I am really tired, should we stop for the night?" "Hold my beer and watch me climb this cliff". Usually it takes about three bad decisions to really get a person in trouble. Typically it is a lone individual, not a group.

The decisions made generally reflect the lack of experience. Along with this inexperience is the usual absence of useful equipment -things like a map, first aid kit,etc.

On occasion we did need to assist those who were well equipped and competent, but this was rare. Quite often alcohol was a factor.

Experience and proper gear develop together. If you are in a new and novel situation, you are at risk to some degree.

I am a good xample. On my very first hike in the Santa Catalina Mountains above Tucson, I found myself caught on a rock sput, with my feet dangling above a forty foot drop that could easily have been fatal. This was the result of wearing grossly improper boots, a lack of understanding the potential hazards, and an uninformed group leader who encouraged us to try our hands at rock climbing (who needs a rope or any of that stuff?)

Tht was the closest call I have ever had. Years later I helped recover the body of a young lady who had flown to Tucson to visit friends, went with them to a popular party spot in the mountains, and suffered a fatal fall. Why her and not me? I wonder to this day....