Elizabeth Warren didn’t lose in the 2020 primaries because her plans were bad, even though some of them were. She didn’t lose because she equivocated about paying for her health plan, although it obviously didn’t help. Finally, she didn’t lose because she couldn’t figure out if she was a bridge between the moderates and Sanders or a Sanders substitute, even though that was a serious tactical error, too. She lost because the electorate in the primaries understood that an elderly, sharp-tongued female Harvard professor was the perfect target for a Trump campaign based on identity and cultural issues. For those voters, Biden was the obvious choice; they were proven right.
For such a brilliant woman, Warren can be incredibly obtuse when it comes to culture war issues. She simply refuses to take them seriously, and takes it for granted that blue culture war activists are on the correct side of history. In that respect, she differs from Sanders, who has come to appreciate that tens of millions of blue collar Trump supporters cannot be reached by an approach based on economic self-interest. His attitude on that point is far more sophisticated than hers.
To put it more simply, a right-wing insurrection based on culture war issues? She didn’t have a plan for that.