It's not that her particular schtick (ever so slightly "left" populist welfare statism) played any worse than any of the other candidates' approaches.
It's that whenever she comes up against a question that requires her to either stand by her guns in a way that might not be so popular and/or doesn't fit with her narrative about her own personal history, or else retreat from her position, she chooses a third option.
That third option is: She lies.
She lies about her and her family's economic situation in her younger days.
She lies about whether her children went to the private schools that she doesn't want you to be able to send your kids to.
She runs from the question of whether her version of "Medicare For All" will require a middle class tax increase, trying to portray it as a matter of "overall expenses" rather than taxes per se until she can drum up a complex but unconvincing lie to cover up the fact that yes, it will require a middle class tax increase.
She's not the only politician who's lying, of course. It's just that she's not very good at it. Her lies are pretty easy to identify as lies.
And getting caught lying so often and so obviously just doesn't mesh very well with her morally superior "I know how to run your life better than you do" Church Lady campaign persona.
In lying contests, the liars who are better at lying win.