In the past, Sumo gyms used to have a quota as to how many foreign wrestlers they could have within their team/dojo.
Recently, those quotas have been relaxed. Due to this change, there have been quite a bit of Sumo wrestlers that have their origins in eastern Europe, Mongolia, USA (Chad Rowan), and even from Egypt (His name in Japanese is Great Sandstorm).
Sumo has had a upswing in popularity due to this new blood being invited into the tournaments. It's been great sports diplomacy.