Madoff was another one with related party transactions and nepotism. If you read Markopolos' memo that he submitted to the SEC, which you can find online or in his book, it's pretty obvious that Madoff was either committing fraud (which is what Markopolos thought) or that he was making money but lying about how he was doing it (which is what some of his customers thought). Some of his customers thought that he was front running orders using his brokerage. But it's pretty clear that the strategy he told the SEC he was using was impossible because his size would've required more than 100% of the volume on that exchange and the other people who trade their didn't know him.
Funny story but I met Markopolos once, and while I do have a low opinion of a lot of the people I met at the SEC, Harry is pretty hard to take seriously if you see him in person. I'll be kind and say that he looked, well, eccentric. His hair wasn't combed, he wore a polka dot tie and was wearing pants with cargo pockets that obviously had a lot of stuff in them. So combine their incompetence with his colorful appearance and the fact that he alleging a fraud against someone who was not only a competitor, which cast doubt on his motive, but who was also the former chairman of Nasdaq. The SEC has a lot of lawyers and accountants, but not finance people or quants. It was only about a decade or so ago that they allowed their registrants to use portfolio margining. And that was only after they lobbied Congress and threatened to move their trading to London or Singapore or Tokyo. So I see why they didn't get it, but just because you're incompetent and not corrupt, doesn't mean that you're doing a good job.
Good luck with the activism, I hope it works out.