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.
I supported her because I thought she’d be a more effective economic populist than Bernie, and wouldn’t get slaughtered among nonwhite immigrants in a general election. Still voted for her in the primaries anyway as a protest against the two-way race between two almost-80-years-old men that the race boiled down to.