Oh, I definitely agree that 1) people don't actually think they're voting for someone who'll make the problem worse, and 2) voters are prioritizing particular values. Single-issue voters are real; I've met many. They all seem to be on the right, however: they have two issues, abortion and guns. There's no shortage of people I've heard say "I won't vote for X because s/he wants gun control", and all other issues be damned. So it's really easy for that party to just harp on those issues and get lots of votes from people who just refuse to think about anything else until they get their way on those. I really do think that, for those voters, candidates could tell them "I'm going to work to ban abortion and eliminate all gun restrictions, and I'm also going to increase your taxes 5-fold while eliminating all taxes for richer people, and I'm also going to help some companies pollute the land you're living on and prevent you from taking legal action against them", and these candidates would still get elected by these people.
However, this doesn't make my initial statement wrong: I said these people are voting against their best interests economically, and it's true. And it's my contention that these people are actually stupid because they do this, by prioritizing a couple of hot-button issues over things that really would affect them personally in a much more profound way than whether other people have abortions (RvW has been around for over 40 years now) or whether they can own machine guns (gun laws in this country are already very lax and no national candidate has proposed doing much to change that for some time now).
I have no idea how you get people to think critically when they've never done it before. The only way I've seen that actually works here is for someone to get a decent education. That just isn't going to happen for some middle-aged conservative living in West Virginia mining coal. Worse, it's not just uneducated blue-collar workers voting this way, there's plenty of seemingly-intelligent people who have bought into very far right-wing politics, for very different reasons than what I mentioned above. Much of it seems to be outright racism AFAICT, like the alt-right websites I've seen lately that rail against interracial dating, pushing racial purity, something straight out of Hitler's Germany.