Remember that Germany was in a dire economic situation at the time (arguably caused by the demands of the Treaty of Versailles) and Germans voted for Hitler because he seemed the only person able to do anything about it, even if the Nazis looked nasty. Furthermore, Hitler lied all the time when it suited him. And to be fair, he DID improve things - he created employment with public works projects (not unlike FDR's New Deal). All with an ulterior motive, of course. Building Autobahns meant there would be good big roads for tanks. Then by the time it became clear he was serious about conquering Europe and exterminating Jews, it was too late to do anything about it short of war. Maybe all that would be very unlikely in a country that's not in that kind of deep mess.
Now fascism was popular in Europe at the time because it looked like the smack of firm, authoritarian government was what was needed. At least in some widespread opinion. Italy got that under Mussolini, and Spain did under Franco when he won the Spanish Civil War (and kept it until Franco died in 1975). The name even comes from Italy - in ancient Rome, the fasces were a symbol of power.
The UK also had the British Union of Fascists with its blackshirts under Oswald Mosley. But I suspect, if nothing else, the British sense of humour had something to do with the BUF not getting very far. Uniformed blackshirts jackbooting around seems comical to the average British mind. I can't speak for the average American mind!
More worryingly at the time, King Edward VIII seemed sympathetic to Hitler and that set alarm bells ringing. There was also much support for appeasement - maybe Hitler isn't that bad really? Neville Chamberlain, as British Prime Minister, thought so, thought he could talk to Hitler, believed him when he said "I have no more territorial ambitions" and famously flew back to Heston Aerodrome waving his little piece of paper and proclaiming "peace in our time".
What an utter berk he looked the following year when Hitler invaded Poland. At that point even Chamberlain realised he'd been scammed and declared war on Germany. And in 1940 the Conservatives chose Churchill to replace him - finally "the Establishment" had woken up to the fact that Churchill was right all along in warning that Hitler was dangerous.
We have the lessons of history to learn from, plus so much more in terms of media to tell us about what a potential leader could be like. So I'm fairly relaxed about it not happening again.