I'm also an ex-Googler, and was at Google when the Rosenberg affair broke. Sergey was nominally head of Google X (the reporting org that Google Glass was in) at the time. Whether he was actively doing anything other than boning his employees is another matter; I had a number of friends in X (including in Glass) and his job largely seemed to be to cheerlead various X initiatives at the time.

And the role of HR and legal is to minimize the company's risk. Just because the risk doesn't materalize doesn't mean the risk wasn't there. The way sexual harassment claims usually play out (if both parties have competent lawyers) is that the company pays out a significant sum of money and then both sides sign non-disclosure agreements and waivers to further liability. The point isn't to go to trial, the point is that the threat of facing a sympathetic jury incentivizes both parties to work out a settlement.

There was one very obvious aggrieved party in to the Brin/Rosenberg affair in Hugo Barra, Android's VP and spokeperson and Rosenberg's ex-boyfriend who quit to head Xiaomi's international efforts right as the affair broke. Presumably Google gave him a generous severance package to not disparage or sue the company, which is why you haven't heard him disparage or sue the company.