The notion that only "superior philosophies" inevitably gain supporters assumes that good ideas always drive out bad. That's not how real-life marketplaces always work, and it's not how the marketplace of ideas always works, either. Remember what the markets for food and medication were like before the FDA?

I'm starting to speculate that democracies become especially vulnerable to fascism during a period when a new communications technology emerges. Hitler made very good use of film/video (it's a cliché that the film techniques Leni Riefenstahl pioneered are still being used today), and Trump is capitalizing off of reality TV and the Internet. I think it takes a generation or two for a society to develop a memetic immune response to the new information vector.