The League of Nations was created with the express purpose of preventing another World War. Ultimately, it proved incapable of succeeding in its charter goal for a number of reasons.
The League was created out of the Treaty of Versailles which only the victorious nations were allowed to participate in creating. This caused problems with initial buy in from other countries. Also, in order for decisions to result in action, there had to be a unanimous vote by fifteen of its members, a statistical unlikelihood. This in effect prevented the league from taking much action.
Global representation was also a problem. The league was intended to encompass all nations, but several never joined. The U.S. was conspicuous absent because congress voted down joining. The league originally barred Germany from joining, since it was an aggressor nation in World War I. It also banned the Soviet Union because communist views were not welcome. How you build global consensus without some of the most powerful nations on the globe is anyone’s guess.
The League also lacked armed forces to back up their resolutions. After World War I most nations were reluctant to use military action or sanctions.
Perhaps Maurice Hankey, the British Secretary of the Cabinet circulated a memorandum. It said, “Generally it appears to me that any such scheme is dangerous to us, because it will create a sense of security which is wholly fictitious"