I conttend that when the slab slipped, snow covered the tent and additionally an upwind supporting ski pile was broken. The group would have to exit the tent, assess the damage, and determine whether they could effect a repair in stormy conditions. This would be hard to do. They would have a flashlight to see with, but even if they could re-raise the tent, it would only be a poor windbreak against cold, blowing and swirrling snow. A fire could not be lit,nor sustained. One might suspect that if the snow slid on them once, it could do it again. There was no need to wait and put in ski boots, the skis were unavailable and without skis, the boots are a slipping hazard. Valenki are better.
One might think they all huddled up and weighed their options, but the evidence suggests they realized that getting out of the wind, dodging a presumptive snow slide and making a short trek to the woods for a fire and windbreak was an achievable priority, so they did it. Only later did they come to the realization that even though they were going down hill, it turned out the trees were farther then they thought. Once committed to going to the woods, only a favorable change in conditions would induce them to alter course. That did not happen. Further, the poor conditions persisted once they got to the trees. An open fire by the cedar was a stop gap effort, but thermally inefficient. They needed the shelter of a ravine in order to try another fire, wait for daylight and work their way back. Tragically, several deadly thingsnwent bump in the night. I feel most of them were falls from a tree and an embankment. Then again, I could be wrong.