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.
Elizabeth Warren's campaign didn't fail due to charisma--have you seen her debate performances? I don't think she was a great candidate (as said above) but what kept her shambolic campaign going until Super Tuesday was her excellent public speaking and ability to connect with people.
The failure of her campaign (which tbh was also the death of basically every other candidate except Biden and Buttigieg, but very egregious in Warren's case) was that she or her staffers made the error of conflating Twitter and journalists with Democratic primary voters.
Rolling out endless plans earned her a wave of press goodwill for a while, but cultivating an academic image designed to appeal to the Twitterati meant that she mostly ended up with a coalition which resembled those people--degreed white young professionals and professors. Not exactly a winning demographic in a primary where she had to win a diverse coalition.
Plus blinking when Buttigieg came for her over healthcare was incredibly dumb.
