The reason they are bringing the whole crew back is most likely cost related. The whole crew was due back in February anyway. They are bringing everyone home a

The reason they are bringing the whole crew back is most likely cost related. The whole crew was due back in February anyway. They are bringing everyone home a bit early; otherwise they would need another flight a few weeks later. And nobody is retreating: there will be 1 American and 2 Russians left on ISS. All of this from the article.