The original article has been updated with Jeff Dean's response, while a member of Gebru's team (who still works at Google Brain) states that Dean's email is misleading and inaccurate: https://twitter.com/alexhanna/status/1334579764573691904
As I understand it: The paper had already been submitted to a conference, and the "cross functional team" Dean speaks of basically reviewed it like peer reviewers and said you have to retract it. It sounds like Gebru and her co-authors were not given an opportunity to respond to the criticisms to stave off retraction. If you've experienced peer review, you know that such reviews are by no means a definitive analysis of a paper, and one usually gets the opportunity to respond. Here, it sounds like anonymous internal peer review was used as a hammer to retract it. Dean's descriptions of the criticisms sounds rather pedestrian to me, as a researcher, and I'm sure Gebru and her co-authors would push back on these characterizations.
Honestly, it sounds like the paper was attacking some sacred cows internally. And Gebru's work probably threatened other researchers on other teams. Not unlike traditional peer review mind you, but at least one can usually post in on arXiv without worrying about this.