Today there is a market for a demagogue - someone whose entire appeal is polarizing, uncivil, personally vilifying, and policy-less. The demagogue's message is "you are weak, but I will make us strong again."
There are always demagogues in the political market. Usually the governing parties are able to shut them out by appealing to the majority who want government to govern according to law. Governing parties then debate policies that appeal to their separate constituencies and reach some compromise.
Now, though, one of the governing parties has created a dangerous opening for demagogues to infiltrate and take over their party structure. By running on a platform of "government is the problem" for a generation, one party has invited to cuckoos to lay their eggs in the party nest. And now the eggs are hatching and demanding to be fed.