And yet we do see conspiracies that lasted decades before someone was outed. Or cases where the information was public knowledge but just never put together well enough for the big picture to be seen (Catholic priest abuse scandal).
I think part of the problem is that people vastly underestimate the ability of 'good' people to do nothing in the face of evil.
It's a history of CIA manipulation of politics and culture across Europe and the US during the Cold War.
Projects like this don't have whistleblowers, because the people on the inside don't believe they're doing anything shady. And some of them don't have much time for the common public anyway.
Historically the extent of the manipulation - through overt violence, and covert forms of persuasion of all kinds, including bought-and-paid-for media influence - has been huge.
I think part of the problem is that people vastly underestimate the ability of 'good' people to do nothing in the face of evil.