Because they are all funded by corporations who want, as Alan Greenspan put it, "worker anxiety" to keep profits high. They gave Trump 37 billions more in the military budget than he asked for - authorising a level spending on par with the height of the iraq war, but will balk at Bernie Sanders's suggestions for universal healthcare or free tuition because it's unaffordable.
It also helps that the republicans are horrific towards anyone who isn't a straight white male: Roy Moore overwhelmingly won the white vote despite talking about how America was greatest during the times of slavery, how he believes all the amendments after the tenth were mistakes(these include allowing woman and black people to vote), not to mention the rampant homophobia.
Trump is the absolute worst thing that can happen to middle America. His policies hit the middle and lower class whites the worst. But they will _feel_ safe and secure with a giant wall and a ban on refugees.