Regardless of where "the problem" started, it was helped along immeasurably by the Repubs. infamous "Southern Strategy" and by Reagan's senile "government is the problem". The Gipper is father to the Trump.

However, the REAL cause was explained by Isaac Asimov some years ago:

There is a cult of ignorance in the United States, and there always has been. The strain of anti-iltellectualism has been a constant thread winding its way through out political and cultural life, nurtured by the false notion that democracy means that "my ignorance is just as good as your knowledge."

Trump, Republi-Trumpism and the Trump Cult in a nutshell.