In order to have prevented WWII, you would have to have prevented WWI. Germans were upset at all the sanctions levied against them after WWI and because of increasing poverty and despair, it made the landscape ripe for someone like Hitler to take advantage of
Hitler was a young aspired guy who tryed to save Germany from poberty after WWI.
He was a hero and saved Germany economy and even american copied his economic strategy.
But, Hitler changed after a lot.