Of all of the man's mistakes, the one that was the worst because it led to the others was that "He made a fire under a tree."
Explanation:
The man built the fire under a snowy spruce tree, then eventually because of the heaviness of the snow it falls down the tree and lands on the fire which leads to the next mistake when the man runs to start the fire again and drops the matches into the snow, and because of the extreme cold and incapable to move he starts the match with his mouth and throw it in the snow where all the matches are, unable to start a fire he finally dies.
