She wasn't a good candidate.
Liz Warren in theory was a perfect candidate ideologically. She was halfway between Biden and Bernie, but she lacked charisma and was a Harvard professor.
She could have run as a non-socialist economic populist that would have had mass working-class appeal but instead went all in on the PMC vote at the expense of the multiracial working-class.
That is what she ran as! She was basically a 21st century version of the anti-monopoly, trust-busting Progressive Republican. The problem is she was getting flack from the left for allegedly having a healthcare plan that was too stingy (remember, if you don't unreservedly support Bernie's specific M4A plan lock, stock and barrel, you literally want people to die), and the Democratic Establishment had been throwing the kitchen sink at her every time she started doing well in the polls.
The market share she was left with ended up being the graduate degree-holding, debt-burdened nonprofit foundation program analyst. The barista in the corner cafe who makes her latte in the morning was voting for Bernie. The overpaid Boomer foundation director in the corner office was voting for Biden.
I think part of the problem is that on some level, there's really nothing that a well-educated, high-achieving, credentialed woman can say that will not be written off as "lecturing" or "nagging."
This is the correct answer. A Republican version would probably work if they hunted, but that essentially it.