But weather decisions aren't really that difficult - the problem is pilots thinking they are better or luckier than they actually are.
Except that in this case things deteriorated very quickly, by all accounts. So the pilot may have been surprised rather than overconfident.
It would really be very frightening to be flying up the narrow canyon and suddenly be entirely in clouds, with downdrafts. Yet apparently that was the situation.
So I'm at a loss for how to prevent such accidents. The risk seems built in given the terrain and the local weather.