In a word, his arrogance. He ignores both the voice of experience (the old man) and the voice of nature (the dog). He violates a basic premise of the world: we are part of nature, not its rulers.
The man's weaknesses that lead to his death are several. First, the man is not prepared for the extremely cold weather he faces on his journey, nor does he take enough supplies with him in case he runs into trouble. He has not dressed heavily enough for the temperatures he will encounter. He also does not take enough food, nor does he take any tools that he might need. Also, he is stubborn. He does not let the dog take the lead when he should do so. The dog clearly knows that they are lost, but the man makes the dog "listen" to him and directs the dog where the man wants to go instead of the other way around. The man is also ignorant. He does not respect the dog or the fact that the dog relies on instinct and is very familiar with the territory and weather.
what is thepurpose of the man waking in the cold