The DNC got wind that AOC might run. They were like “fuck that we need to get ready to shut that shit down.” So Harris must have been nudged to make a statement.
Remember: the democratic establishment wants someone slightly more electable than Hilary and equally unlikely to make any meaningful progressive changes.
While the republicans want to actively wreck society, the democrats want to just go back to the un-newsworthy background grift where the news can get back to reporting on cloned sheep and panda swaps.