It's crazy that huge segments of the population are buying into it. And it's not just Trump, there's also the anti-EU agitation that Russia is supporting in Europe - and probably plenty more. People fall for that as well.
Why on earth are these tactics working, and why are it always the people with the - let's say - nationalistic preferences that get riled up into a frothing mess by such means?
We have a more serious problem than just this single thing. People just can't fucking help themselves. And that is despite thousands of year of recorded history full of brutally-clear warnings about what happens if you don't pay careful attention to what you're doing - especially as a group.