They understand good god damn well they don't work. This is exactly the plan. Sell people on the idea it'll help them, then these companies take the money and run.
What amazes me is some working people will continue to vote this way even though it keeps failing. I guarantee there will be more tax cuts sold in the very near future, and the same people will buy into it. Some people never learn.
It's hard to learn when your sole source of news is Fox News.
It's not even that Fox News is an outlier, the fault is ad supported news media. What do you think will happen when a politician comes along that threatens the million dollar ad accounts from finance and health industries through policies that reduce those institutions influence? Chomsky was right (see https://en.wikipedia.org/wiki/Manufacturing_Consent).
I would bet if you actually look another layer deep you'd find out it has nothing to do with "the media," ad-supported or not. I think you'd find a lot of people have little use for (and little interest in) the truth, and therefore voluntarily seek out a fun us-vs-them worldview with a group to hate (on both sides).
Eventually you end up with an anemic government that overspends on things that don't work and ignores all the social programs that the government put in place to prevent history from repeating.
I don't see the left looking to educate the public against Fox News in general. As long as Fox News controls the message, the uninformed will continue to vote against their best interests. If someone ran a FB campaign against Fox News, I'll donate.