I agree with the piece's general tenor, but I think the author is going overboard here:
I strongly suspect that the above is only true if you add,
when running against a high-profile Democratic nominee with high negatives who runs a bad campaign. And probably another conditional, and
when no one realized how terrible President Trump would truly be.
Maybe I'm wrong. And maybe the Democratic Party will uselessly chase it's own tail and nominate another poor choice to be nominee. But my prediction is that anyone who thinks Trump's victory was more tactical than circumstantial, who thinks that mobilizing American Nazis and their fellow travelers is going to be a successful strategy for winning elections, is going to be disappointed. (Assuming we still have elections. They are Nazis, and following the Hitler route will doubtless come naturally.)