This is a question I've heard asked from time to time since I was a child. Nobody really knows why, at least in the public school systems and among the ordinary Americans who don't study history.
So here is my two cents.
All wars are banker's wars. After the Rothchilds came to power. Watch Europe The Last Bast Battlke for a good history on this subject as well as the documentary "All Wars Are Banker's Wars" you can find on this site.
The historians and others have lied a lot about WW II and Adolf Hitler. They don't tell you that the Bolsheviks were committing atrocities against the German people like Lenin's did against the Russians. They don't tell you that it was the bankers who goaded him into war out of fear of Germany becoming an economic powerhouse. And other stuff. And they do their best to make him out to be the bad guy who started WW II when nothing could be further from the truth.
The Treaty of Versailles, from WW I, was designed to force Germany to pay for the costs of WW I. This pretty much destroyed its economy. There so much inflation that they were printing too much money to pay for it, and the bills were getting into the millions. And the historians don't tell you that the Allies were breaking the Treaty themselves trying to take important land away from Germany.
So Hitler used secxret means to help rebuild the economy and the military in order to get around the treaty. This had the effect of getting the German populace back on their feet again.
So why would the German people love Hitler and allow Germany to become Nazi Germany?
Because he got them working again, got them food on their tables to feed their families, and roofs over their heads.
He was a patriot who loved Germany.
But most people will lie about it,.
So there's my two cents.