IMHO, two things: (1) The gradual destruction of labor unions. When I was a kid, labor unions were strong, seemed like every adult was part of one. And there existed a "brotherhood" amongst the various unions. When one union went on strike, the other unions would wholeheartedly support them. And (2), pro-business bias in reporting (don't wanna upset PepsiCo, a massive sponsor!). Here's a great example: https://www.google.com/search?q=frito-lay+strike+site:foxnew... . Nothing about the Frito-Lay strike. Fox News is the ONLY news source in Middle America. I don't feel like other major sources are much better; they've got sponsors to please, too.
While I understand your point about the popularity of Fox News in middle America, it's a big stretch to conclude that it's the only source. People have to start taking responsibility for which sources they read, listen to, and trust. There's nothing stopping these people from showing a bit of initiative and reading a broader range of news sources. Well, nothing except their passivity and desire to be spoon-fed news and opinion that correlates with their pre-constructed worldview.
