It's worth keeping in mind that is already being set up as a 5 season series, so just because something appears to be completely unrelated at this point, doesn't mean it won't tie back to what's going on in other parts of the show.
Game of Thrones is a perfect example of this, the show started with several stories in different parts of the world, but as it went on they started weaving together more and more.
I have a feeling by the time we reach Season 3 or 4 we'll see The Stranger standing side by side with Galadriel, Elrond, Isildur and Elendil as they're fighting Sauron's forces.
I did.