It's already been said, but the demographics are likely changing. Once you get industry that leaves the area, more affluent and educated people usually follow the jobs to other places out of state.
What you are generally left with is shrinking metro cities, a more rural and uneducated populace, less jobs, and more poverty.
Those blue collar manufacturing jobs in Rust Belt cities are gone, and they aren't coming back. Most of them have been lose to automation and export overseas.
These Republicans craft themselves as the religion and working people's party, but they also dog whistle racism and classism. They also fall back on Christian founded beliefs such as being pro-life, opposing gay marriage, and the cutting of entitlement programs that many of their supporters think only benefit minorities.
Most people default to blaming someone else for their problems instead of looking in the mirror at themselves and citing their own incompetence, lack of education, and lack of knowledge for their predicament.
Republicans play on that perfectly to rural Whites that need some Black, illegal immigrant, Muslim, or poor minority to blame for their problems.
The progressives and liberals are painted as socialist that want take away their most basic rights even though America thrives on socialist programs like public education, public hospitals, social security, banks backed by the FDIC (Feds), state highways and interstates, etc which are ALL socialist programs by nature. Feed them an enemy they think they're better than and also paint the perceived enemy as part of their problem and you can easily manipulate them.