WWI was so much more brutal than any war before because of chemical weapons, mechanized warfare and the sheer scale of death. It also caused immense psychological damage on those involved. It seems like any sane person who had witnessed the war would have no desire to for another conflict to even potentially begin. Even with notions of racial and national superiority these people knew the damage their enemies could do. So why then did the officers choose to fight another war? I'm more interested in middle command than the high command and newer officers.
The German Officer Corps had been thoroughly saturated in the years leading up to the Machtergreifung (Hitler's Bid for Power) with the Dolchstosslegende or Stab In The Back Legend, which I discuss [here] (https://www.reddit.com/r/AskHistorians/comments/2s1g5g/ive_read_that_hitler_blamed_jews_largely_for/). In short, the German Army had been running the Empire from September 1916 until November 1918, and many (esp. Ludendorff) were convinced that Germany had not been 'properly' defeated, if defeated at all. They determined to study the war, draw lessons that would enable them to fight it better than they had before, and ultimately see the rise of a leadership that could forge a proper, militarized, Volksgemeinschaft ('People's Community') that would stave off defeatism (weak-willed civilians were among those blamed for defeat) and win a future war. Ultimately, the Army, thanks to the efforts of men like Max von Hindenburg and Reichswehr chief Hans von Schleicher, got their wish, in the form of Hitler (though Schleicher was assassinated during the Night of the Long Knives as a potential rival to Hitler).
John Wheeler Bennet's The Nemesis of Power is a classic account of the German Army from the end of WWI to the outbreak of WWII.