The US invested so much effort into this because they were worried that their own agents were involved with the theft. This was all part of their effort to clean up the massive corruption post-Silk Road seizure.
It does sound like the history of corruption from 2013 means they have to stay alert to this problem.
And it also sounds like the revolving door of government has allowed a lot of the former investigators to get high paying gigs at crypto scam outfits. Not a good look.
Overall, it seems like the government dealt with the corruption adequately, however. It is not reasonable to assume that any institution will be free of bad actors. The question is whether those actors are punished or not.
I have become tired of the overly cynical and hostile rhetoric directed at law enforcement, especially just lazy stuff. But this thread was thorough and fact-based.
So, one agent was caught and convicted of theft, on an unrelated matter, and this is evidence of corruption? Wouldn't that, in fact, be evidence of a system that is successfully punishing corruption?
And since the transaction history is traceable, you cannot posit mysterious other transactions that are unaccounted for. Those would be quickly revealed.