Also, those people have learned otherwise long ago, and have modified their approaches and recommendations, while Trump doubledowns on downplaying it.
That being said, Trump was supposed to lose just as bigly in 2016. Hillary was supposed to win then, as she was supposed to win in 2008, and Mitt in 2012, and Gore, Perry...
The DNC once again forced someone down the base's throat because he was the safest surest bet because no lessons learned in 2016. Other than not taking certain States and demographics for granted this time, they're making the same mistaken assumptions and mistakes as they did then.