League: a group of sports teams who all play each other to earn points and find which team is best. major league baseball. United were league champions last season. If we look at the league table we can see Bolton are bottom with 21 points.
The above paragraph is Oxford Dictionary's definition for league. The first part in bold doesn't make sense to me. It is not clear whether it says champions were united last season? Or that United club was (why were is used if so?) champion of the league last season.
Also, why is Bolton written with are rather than is?