According to her, she was recruited by Jeff at a conference specifically to work on improving Google's machine learning equity. As part of hiring somebody, I don't just meet them at a conference and read their papers. I interact with their prior employment network and read their social media. I think if Jeff had paid any attention to her tweets before she was hired, he would have thought twice about bringing her on.
I wonder if anyone's compared Timnit's firing to Apple's firing of Antonio García Martínez. It sounds like both are politically opposite versions of the same mishire situation.