Why did the League of Nations fail during World War 1?

The League of Nations was not formed until 1920. Therefore, it had no bearing on World War One. After the League was formed, it failed and a case can be made that if the US had joined the League, it would have been a more viable organization.

Sanctions against Germany were too severe resulting in severe economic hardship that caused the German people to seek an alternative. Hitler, although a bad choice, was perceived as their only option at the time.

Which war?

The League of Nations didn't even exist in WW1. The above answer is off topic and meaningless.

The league of Nations DID exist...

In an effort to avoid future destructive conflicts, at the end of WWI, the diplomats who gathered for the Paris Peace Talks created The League of Nations. Their main principal, of course, was to maintain world peace. The league had two major flaws that ultimately caused it's failure. First, was the lack of power it held to enforce decisions made by the league. Second, it relied on collective security as a tool for the preservation of world peace. The basic premise underlying collective security arrangements was the argument the concept that aggression against one state was considered aggression against ALL states, which had pledged to aide one another.