The people in the Rust Belt don't think the Rust Belt jobs are ever coming back. Nobody does.
Nobody believed Trump when he said he was going to save factory jobs. The Trumpers just heard it for the coded message that it was. "Yeah you and I know that factory ain't never gonna open up again, I'm just here to punish the people who did it, the people you think did it, the people you already hated and now are using this as an excuse to hate, everyone who's better off then you and you're jealous, and hell while we are at it just everyone you've ever wanted to punish for whatever reason."
This is why people are so confused when Trump outright says to his supporters "I'm going to do the thing" then doesn't do the thing and they still love him. Because they didn't hear "I'm gonna do the thing" they heard what he was actually saying "Listen we both know I can't do the thing, but me pretending I'm gonna do the thing is gonna troll the libs soooooo hard and isn't that just awesome?"
Trump didn't tap into some hidden well of hope in the rural areas and the heartland and the rustbelt that things were ever going to get better and he was going to lead them to it. This is spite and revenge and... just raw uncategorized, unorganized lashing out. It's not hope.
The rural areas of America haven't pinned any hope on Donald Trump, that's ludicrous.