Re: why are they not being treated as accessories?
Full analysis takes time, and you also need many "runs" so that you can trace the paths.
If they had blown the whistle PDQ, they could have gotten a fraction of the people running the scam, by letting it run for 2-3 months (and presumably logging the transactions, frauds, and scams) they nabbed the whole "company" and have records that could cause the victims to claim restitution.
Also, if watching, investigating, and gather evidence counted as accessory, then every LEO ever would also be guilty.