She's corrupt af and connected to Ivanka and Jared. She knows it's very improbable she could get the nomination, and impossible she could be elected president. She is just acting as spoiler to take down the only candidate likely to defeat Trump.
When trolls online acted against Hillary the same way she did against Biden, everyone said they were Russian bots.
"on behalf of herself" -- Do you mean self-interest, or out of a sense of moral indignation?
If you're implying the latter, you obviously do not know much about her career, about the reality of life in San Francisco for marginalized, impoverished, and homeless people WHICH SHE ENFORCED AGAINST THEM, or about her lack of anything resembling a human moral sense. Speaking from a position understanding the reality of suffering in San Francisco and California, I would call her the only candidate in the race who is arguably more corrupt and objectionable than Trump. California is near qualifying as a failed state by global terms, and the streets of San Francisco show the same level of abusive human degradation as the most impoverished cities in the world.
Why would Harris be pretending to be "outraged" about Biden, while this is the same exact Joe Biden who was chosen to be vice president by the first black president, without any controversy whatsoever?
I do not especially like Joe Biden, I just want to defeat Trump.
Regarding self-interest, even that qualifies as a sketchy hypothesis, since she and her campaign obviously must realize she would be dead in the water against Trump in Wisconsin and Pennyslvania. It's unlikely but not implausible she could get the nomination, but being from the Rust Belt I can see she is an even weaker candidate in that region than Hillary Clinton was.