They get a pretty unfair rap over this. People talk about Chamberlain being an ‘appeaser’ for instance, but they neglect to mention that it was only 20 years after another world war which had cost tens of millions of lives, and as a result there was basically zero appetite in Britain or France for another huge war. Democratically elected leaders can’t just mobilize their country if the country doesn’t want to be mobilized.
Also nationalism and blaming foreigners was more of a default position back then rather than some crazy exception. The world was largely incredibly racist and nationalistic, including the eventual Allies, with anti-semitism in particular being rife. There was also much less of a globalistic attitude. When Chamberlain talked of ‘a quarrel in a far away country between people of whom we know nothing‘ he was describing a feeling shared by most British people. The vast majority didn’t have any real lines of communication with other countries, didn’t travel overseas and only knew what little bits of information they read in newspapers or heard on the wireless. Would you send your kids to die in a place you’ve barely even heard of, to help people you feel no connection to and know nothing about? The public attitude was much like the American one later, let the foreigners sort out their own problems. It’s only in hindsight that you can see what a terrible mistake that really was.
The real danger signs with Hitler were his refusals to conduct international diplomacy in the normal way, breaking agreements he’d previously made, and using strongman tactics to try and force countries to comply to his demands (any of this sound familiar in the current political climate incidentally?). The problem with the timeline however is that although he was acting quite irrationally, most of those warning signs came after Munich, not before. When he broke the Munich Agreement it was the first concrete sign that he was not just a hardline populist, but actually someone who could not be negotiated with.
Incidentally, an interesting small historical fact that tends to be forgotten is that both Poland and Hungary annexed parts of Czechoslovakia as a result of Munich. It gives a little more relative insight into the attitudes of the period, beyond the simple ‘good guys/bad guys’ picture.