I’m not USian, but from what analysts worth their salt would say, it is combination of-- but not limited to-- intentional dumbification of Americans, the opposition not really being opposition, the US Supreme Court legalising bribery, the atomisation and polarisation of American communities, de-industrialisation, growing wealth inequality and general corruption. These contributed to the growth of frustration and populism among the voters to vote for anyone who is “not establishment”. Someone who “tells it like it is” unlike most politicians who always do politician speak. In the minds of many Americans, Trump may be a grifter and a pervert, but they see him as genuine. If the democracy is a sham after all, might as well pull down the mask and show tje country for what it truly is. That’s why people say Trump is a symptom, not the cause. The same symptom is happening across the world which is why we’re getting the same far right populism.