The popular consensuse after WWI was that ambitious elites had funelled the world into war seeking the glory of a previous age. And in the end, average people paid a terrible cost. Due to their ignorance of the changes in mobilization and military technology they embarked on something frivolous that in previous centuries would've only touched a few but instead created misery across several continents.
There was an intrinsic logical reaction. Most cries for national glory and exceptionalism should be ignored. If there wasn't a direct benefit to the widespread populace, war should be avoided. This reaction is most evidentary in how so many European countries significantly democratized after the war with most monarchies disappearing or being sidelined completely to honorific status.
The lessons of WWI couldn't have been timed any worse (though this doesn't make them wrong). The intent and tyrannay of the axis powers are fairly unique in history (I only know a few as totalitarian, brutal and empirical as they; the Assyrian Empire comes immediatly to mind). Their kind is not common in world history. It was easy to see Hitler as just another would be king who might goad the world into conflict but might also receded if not attended too.
Edit: Bruce Carlson did a fantastic set of podcasts examining Neville Chamberlain's peace efforts. I think you have to pay for access to back episodes of his show now but they are well worth it.
