The Lend-Lease Act: Questions

Was WWII necessary? Was there ever a point where Hitler's militarism could have been headed off by diplomacy? If it was inevitable, when did it become inevitable?
Were WWI and WWII really different wars? Or was the second a continuation of the first? What were they really about, deep down?
Why did the different variations of fascism have such broad appeal across Europe among different nations and cultures? Is there some sort of fundamental fascism?
What would have happened if FDR lost an election to a pacifist candidate? What if the United States hadn't supplied the Allies or contributed troops when they did?
For people who despise war and hope for world peace, what is the lesson of WWII? Is it that war is sometimes necessary? Or that true pacifism roots out the causes of the "necessity" of war in the first place?