You know what struck me about that paper (after I got over all the personal paper quirks) they basically canonized Trump as a "moderate candidate" rather than address it even though their own 2020 survey showed that not even Republicans consider him one.
If we award Obama and Hillary a similar score in their ideological chart as Biden just to be simple, and shift Romney/McCain towards the moderate from Trump. Then 2016 already broke the 2000-2012 mold of moderate vs. moderate. It was moderate vs. radical. And then 2020 isn't radical vs. moderate but radical vs. radical, by their own measures. Applying theories and models dating back to 2013, or even 1957, wouldn't account for this.