Their mandate isn't to maintain the social and economic order like a verbatim press release from the Communist Party of China, their mandate is investor protection. They have tools and a wide degree of discretion, and that doesn't usually mean crashing market sentiment.
Now the question is - What is the SEC's bottom line to start pursuing some kind of investigation or indictment?
The only action till now, as far as I know has been one of the outright frauds: https://news.ycombinator.com/item?id=15370631