Scientists would find it difficult and perhaps pointless to try to prove an explanation, but can make some educated guesses.
All canids, that is, wolves, coyotes, dogs, etc., typically circle before they lie down, though not every single member of all species will do this.
The old assumption was that it was to stamp down grass, but of course it would also work very well to make a little depression in dirt, or particularly snow, to get under the surface for protection from high winds in winter.
Or the circling might be preparatory activity, simply feeling out the ground for sticks or rocks or checking for enemies.
Dogs often circle, lie down, stand up and move someplace else.
It is not a rational process, but instinctive experimentation, because dogs apparently don’t have the brain power to look and think, “This looks comfortable, I guess I’ll lie down here.”
Instead they feel it out with their feet.