The Rural areas DON'T THINK THINGS ARE GOING TO GET BETTER.
They aren't (that kind of) stupid. They know (usually, on at least some level) that the factory jobs and the coal mines and such aren't coming back.
No of course they bloody didn't think Trump wouldn't actually bring them back. That ship sailed. A lamb bleating "But I don't understand, Trump isn't making things better for them" is missing the point by a rather large margin.
They are happy because "the others" that didn't get left behind are being hurt, that's all. If the last 4 years have taught us anything is that's "spite" is a much bigger mover and shaker in politics than we previously wanted to admit. And it slots in nicely in a post-fact world, which is why that's been such a big push from the Right.
Again they are not waiting for a savior to make things better for them, they are waiting for someone to sink the whole boat because there's not enough room on the lifeboats for everyone and they'd rather we all gone down then just some of us. And Trump very much has at if not sunk at least put some holes in the boat that are going to require major damage control.
Again 2016 was a game of inches in very few areas so 2020 could very well swing the other way, but without addressing this issue on a base level in a way that the rural areas accept regardless of how much we like or agree with it we're going to do this dance again, maybe with someone worse than Trump.