Is it really just a bunch of elite politicians deploying a strategy of manipulation on their voters? Or do the voters themselves feel locked out of their own government and need a rationalization to justify their feelings, something politicians are happy to provide?

This is what I think as well but often cannot well put it into words. So much so that it is probably the only way I can justify to myself how someone like Donald Trump would even decide to run for president at all, then go on to win as a Republican. He wasn't a politician and wasn't even really a Republican. As much as he gets mocked for it, he's just pretty good at winning things/money/arguments/property, right?

He saw an unaddressed desire for someone like what he maybe had the capability to push, and has the innate ability to ignore the ridiculousness of it, like some savant tech mind might push through doubt and ridicule to make an unimaginable or untried idea work with plain old confidence. And he made it all just work in a way that gave that angry majority what they seemed to want. He saw that there was a portion of this country that was angry, hurt, and in fact a slight majority of the population seen from the right angles. Everyone else had been ignoring their voice so much that people can admittedly forget they exist in a political arena. And he gave them what they wanted, whether he agreed with it or cared about it at all. didn't matter

I don't mean that he was a visionary or a genius, though I don't think him an idiot. Surely others were making their way to this conclusion. The divide was growing and politicians were entertaining catering to a far-right majority... but he muscled this idea all the way into reality. And now it is.

I don't like or agree with a lot of these wants and desires of this US majority (or near majority) and it's easy to take out aggression on a leader. But you are exactly right, we need to figure out why so many people in the US think how they think or want what they want. They are a real and significant portion of this population and have a real voice of their own. They are Americans. How are they hearing such different narratives or as you point out, why are they creating them?

It's a pretty big deal right now.