They blame the other half of the country for calling them “deplorables”, immigrants, globalization, religion, gender, education, science, and anything else that is an easy scapegoat. Blame whoever you want but the symptom of this illness that the institutions failed to resolve is the current political reality.
But then the question is: why?
Protip: if your answer is something like "they're degenerates," you're just pompously congratulating yourself, having no empathy and knowing and learning nothing.
Conditions were created, and allowed to persist, that shouldn't have been tolerated. The political system failed, and recent events are just a symptom of that failure.