What is it about the stranger that Captain Walton finds so interesting and appealing?

Walton begins to spend time with the stranger. He is morosely unhappy, and when Walton talks about how he might be sacrificing his life on this expedition for the sake of knowledge, the stranger breaks down and decides to tell him the tale he has kept secret in order to reverse that opinion. He is highly motivated and in his prime, a younger version of the weathered stranger, who had the same ideals at one point but has had to relinquish them. Walton sees himself in the stranger.