On this thing about 70% of republican voters still suspecting that Obama is not an American, just anecdotal but true - my nutty auntie in Floria is one of them. This is partly because she's a racist nutter, but also because she gets all of her information / news from a tiny echo chamber of extremist friends on the internet.
I think that's a part of the story which hasn't received as much attention as it warrants and a defining characteristic of the time we're living in:
The majority of Americans (62%) say that social media is where they go to get their news, with Facebook the number one source of information. This is true of my auntie, and she's 71.
So of course people will be mainly just confirming their bias, sharing with their friends the things that reinforce their existing views.
It's not about stupid its about how the proliferation of information has led to people consuming only very selective views, filtered by their social media networks so their prejudices are reinforced. Which goes for everyone of course, not just republican voters or whatever.
News Use Across Social Media Platforms 2016
Facebook’s failure: did fake news and polarized politics get Trump elected?