To encourage disarmament. This meant SLOW progress. Great Britain, France and Belgium invaded and forced Germany to pay. Britain and France were too afraid of war and did nothing to defend Abyssinia.
They housed, fed and dealt with over a million Prisoners of war. The League helped Austria and Hungary with their struggling economy. To make the world a better place by improving people's working conditions and by tackling disease. This created a hostile Germany, which although also joined in quickly left after the rise of Hitler.
However, the League also had great weaknesses. The League significantly cut down on leprosy and malaria which could have killed millions of people.