I think that, as much as anything else, Trump's popularity is just an outlet for many people to show their outrage that has been building up for a long time about the way the political system has been run in this country. Different people are disgusted over different things....but there is widespread, pent-up outrage out there today. Some people are disgusted about the way money controls the system. Some people are disgusted that in spite of all the senseless firearm killings, nobody ever does anything about the ridiculous number of guns readily available to almost anyone...including assault-type weapons. Some people are disgusted that the welfare state is totally out of control, with widespread abuse everywhere. I could go on and on....but the point is that many Americans have reached the tipping point and their frustration in many cases is being manifested in support for Trump....no matter what he says or does. Obviously, Trump would be a disaster as president....but, evidently, many people have reached the point where they no longer give a damn.
I don't know what the answer is, but I don't think there is any question that much of the "system" is broken and nobody in congress seems to either know how or even care to try to fix it. Everything is like a political ballgame now....and because of gerrymandering...compromise is out of the question. Too many districts....on both sides....are now construed so that the biggest problem to remaining in office is a challenge from a more radical candidate in your own party. And that has led to worse & worse "governing" by our elected representatives. Many people have finally had enough.
Donald Trump isn't the answer.....but neither is Hillary Clinton. That's the problem facing the country today.