Thanks. Indeed, this is why I often say in my writings on Trumpism that while we shouldn't sugarcoat the monstrousness of these "populists" and trolls, we as liberals or progressives should recognize that our failures likely help set the stage for this reckoning.
The right-wing demagogues on TV are indeed catering to a market demand, which is what they're supposed to do on liberal, capitalistic grounds. In the big picture, capitalism is as liberal as democracy. You seek profit, by fulfilling a demand.
Granted, the product in this case is toxic because of the diabolical invention of infotainment. If the education system were sturdier (another failure of capitalism and big government), we'd be able to tell the difference between knowledge and entertainment. If Fox News and talk radio were more widely recognized as just entertainment, folks wouldn't take them so seriously. Trump's fan club, then, would resemble Harry Potter's. But the right-wing sophists and public relations experts are savvier than the idealists and purists.
And perhaps the problem isn't that lots of Americans are so gullible, but that they're eager to suspend their disbelief because all they have left are fantasies. The neoliberal "establishment," including the late-modern institutions of democracy and capitalism has failed them that badly.