A simple theory deriving from the discussion "Re: Murdered for entering into a sacred place" but that brings a clean unfolding.
What about a herd of reindeers? The area is still populated by the last remaining wild herds :
https://www.ipae.uran.ru/sites/default/files/publications/Ранюк%20М.Н./Korytin_2001_2_eng.pdf
The antler on pole could signal the entry of a very special hunting zone (or on the contrary the zone where the herd cannot be hunted), where a "mythical" wild herd roams.
Things happen like this:
+ Herd (200 or so animals) is hunted (by men or animals, or just on the move) from an opposite side (from where the group came or where it is going) of ridge and crosses it running, tramps the tent (do reindeers do that if not frightened? maybe they didn't see it since it was half sunken in snow), leaving it in chaos and with some people with heavy injuries (head, ribs)
+ since the tent is ruined, group decides to go to the tree line (maybe it's middle of night, wind has calmed and clouds are away, and they can see the trees very well) to find shelter. Four of them are already outside (they heard the rumble noise of the herd approaching and went out to see: they will be directly hit by the animals and so are the most injured), those in the tent have to make a cut to get out, skis and poles are broken by the herd passing over the tent (maybe just one animal could do it, otherwise it would not be standing at all)
+ they make a "den" for the injured and leave them there. The 5 other start a fire that will be a landmark to come back to, 3 go back to the tent but run low on adrenaline and cannot make it. the 2 at the fire are worried about the wounded and give them their clothes (they think the fire is enough to keep warm, but it isn't and even stops: they die believing the 3 are on their way back)
+ no explanation for radioactivity (even if i like the isotope tracking of sensible personnel by kgb as a good one), or "mutilations" (birds ate the eyeball and tongue rest of body was too frozen ?)
+ why footprints and no sign of the passage of the herd? because the herd was going along the slope towards (or from) the pass where snow was hard: reindeers would not run in a direction with "ravines"
so, no murderers, no military, no ufo, no lightning ball, no lying Mansi ... just a natural (reindeers) compelling force