They hired Gebru as a professional thorn in their side. "Come up in here and be a pain in the ass! Tell us what we're doing wrong!", they said. "We're Enlightened Corporate America, after all!" She is a chess piece in the game of Wokeness Street Cred.
She then proceeded to do the job she was hired for, and now they're all "Hey lady, Here At Google that's not how we do things".
That said, as a manager, I would have "accepted her resignation" and/or fired her without hesitation.