no mtb experience but plenty of hiking/peak-bagging experience in lots of crappy conditions. the ride/mountain will always be there tomorrow.
i can count on one hand the times i turned around because it just wasn't worth the pre-strava "epic" hike/ride. i was always glad i turned around.
it's one thing if you know you are fully fueled, hydrated & equipped for such a ride/hike. it's another thing if you are just trying to be a hardman.
in crappy conditions, you have to have all your wits about you and be prepared to turn around any second-not minute. a true shame this happened.