Russians, crazies, Ufos, aliens, bigfoot, other cryptids: take your pick. Having had my share of the bizzare in the woods over 40 years, anything is possible.
LEMMiNO does a really good analysis of this. He concludes they left the tent due to their homemade stove malfunctioning. A combination of smoke inhalation, CO exposure and alcohol intoxication lead them to believe the tent was on fire / beyond salvaging. They died quickly, some looking for shelter in the nearby woods (killed by a small avalanche taking them over the edge of a ravine), some trying to stay warm around a small fire they'd managed to build, and some trying to return to the area of the tent to retrieve anything useful not consumed by the tent fire.