It's kind of remarkable that they kept the lid on this on long as they did. With so many local/loosely-related agencies involved, I'm surprised somebody didn't leak this much sooner.
Yes, I find it VERY hard to believe that this went on and nobody mentioned it at all. Not one disgruntled employee, not anyone mentioning it to a friend at a bar? No way.
Now we have proof. So that's that.
Also, given the strong "disincentivization" for whistleblowing that is going on at intelligence agencies, I am not at all surprised that it took a few years before somebody went public with it.
Hell, it used to take decades before this kind of stuff became public. Just this year we were made aware that the West German spy agencies opened _all_ cross-border inter-German mail. You know, the kind of thing that we in West Germany were told only the East Germans would do. That was kept secret for more than 20 years after it stopped being done, even though thousands of people were involved.