Since the SEC generally processes cases in the order which they were received, it can take a long time for them to even look at a complaint or suspected fraud.
But once they do they can act swiftly to protect shareholders if wrongdoing is conspicuous.
SHR* was suspended VERY quickly, and Kevin Harrington of Shark Tank fame was reportedly involved with that one.
The message board indicates that most investors didn't begin to suspect trouble until July 2018 (even though the stock had already been temporarily suspended).