Apparently HR did an internal audit and found no evidence of retaliation. Which isn't surprising. It just means that for every decision made by a manager in this case, they had a reasonable business justification that wasn't simply a desire to retaliate.

And that's the rub, because this cuts both ways. On the one hand, it's easy enough to come up with a non-retalitory justification for just about any decision. But on the other hand, when an employee puts themselves in this position by speaking out so visibly, then any negative eventuality is going to feel like retaliation. I honestly doubt there would be a distinguishable difference between retaliation and just the normal churn of business. It'd be impossible to tease out the underlying causality. Especially in a company where projects involving hundreds of people are regularly spun up or torn down with only a few weeks notice.

Certainly Google has a disproportionate number of people speaking out internally about the company, either opposing or in favor too any particular outcome. The company culture encourages and rewards this sort bottom-up decision making, to the point that it's relatively common to see the company change course on one decision or another based on the kind of vocal dissent that at most companies would get you fired.

Certainly plenty of people who speak out in dissent continue their careers as normal. Others leave in frustration. If there's a pattern here I certainly don't know what it is.