She did very little to separate herself from Biden and alienated her base trying too hard to appeal to the right. She wouldn't even take a stance against genocide.
One of the biggest dysfunctions (possibly intentional) in America's two party system is that the "left" isn't really leftist. Both parties are pro police, pro military, pro American imperialism, pro oligarchy and anti labor, and the politics of both drift to the right. The red team just happens to be far more right than the blue team.
And Kamala Harris didn't prove an exception to the rule. Voters didn't want to vote for the status quo, no one really liked Biden, he was just the only option besides Trump. But that's all she represented. Just "not Trump."