> Did the whistleblower reveal something we didn't know already?

A lot. The resulting Wall Street Journal series directly led to the shut down of Instagram for Kids.

I see it as similar to Snowden, in the sense that everybody kind of knew (actually guessed) but now we actually know. It doesn't come as a shock, but it's important information to have since it can be now argued with authority.

The whistleblower revealed that Facebook knows it is bad for society. The documents also show Facebook actively optimizes its algorithms for "bad for society" content because that drives engagement which makes them more money. Furthermore Facebook doesn't do as much content moderation in regions/languages with low usage numbers because it costs more than those users make them. So calls for genocide in Myanmar basically go unchallenged and unmoderated because Facebook doesn't make much money in Myanmar. Sorry genocided minority, you should have been more valuable to Facebook.