Some of the others were able to dig out a "den," start a robust fire that lasted at least an hour, and take clothing from the bodies of the "two Yuris," but these three couldn't even get to the tree line?
I don't think the 'den' can be regarded as fact. The branches with 4 pieces of clothing on top might have simply been laid on top of the snow, perhaps in an area with some wind cover.
In fact if they had a den, it would be highly unlikely for them to end up outside of it, all of them near each other. If it collapsed, some might not be able to dig themselves out and would be found on top of the branches. If it didn't collapse, how did they sustain their injuries?
That they started a fire is more likely, but again is anecdotal, as far as I know there is no photograph of the fire's remains. Presumably these were found under snow.. however due to all the other Mansi items found near the cedar under snow, it could be that the fire predates the Dyatlov group and was from Mansi hunters who have been there months before, or... weeks after the incident. Or the half-burnt tree branch might have been struck by lightning in a storm and is not from a campfire.
However, I wouldn't concern myself too much with this, one way or the other, because it doesn't interfere with the most likely explanation of the "incident."
The most likely explanation of the incident being?