While I totally agree with you that most conspiracy theories are complete BS, and I hate to say anything to give them any sort of credit, I have to disagree with your premise.
We as a nation have kept massive projects secret successfully on many occasions (only having the public learn about it after its made public many years later). In fact they are masters at doing that and use many techniques including compartmentalization to make it possible despite the incompetance of individuals.
In short the ability to keep large operations secret is not just theoretically possible, it is proven to be possible (manhatten project for example).
what keeps us largely from having such massive conspiracy theories that are harmful to society as a whole but beneficial to an elite few isnt so much incompetence to keep secrecy... its the general morality of people. Truely evil people are rare, and people will only keep a secret effectively if they feel it is morally justified. If the people working on the Manhatten project felt it was contrary to the greater good of society as a whole they probably would have leaked the secret , or atleast, a small few might have.
There are **plenty** of large top secret projects kept for longer than 3 years. I dunno what to tell you, but anyone who has worked on top secret stuff knows well that the government has little trouble keeping large secrets over long periods of time.
Also since we are talking about some conspiracy theorist supposidly claiming this or that is happening, then it isnt kept secret, if it were true every single conspiracy anyone ever claimed happened was one that was failed to keep secret and was leaked. So its a bit of a moot point since they are specifically asking you to beleive something that WAS leaked.
@freemo @SecurityWriter
The Manhattan Project was secret for ~3 years. That's hardly an inter-generational cabal. I don't believe those types of projects map into the same space as these notions of sprawling conspiracy.
Plus the project was very physica and it was the 1940s. I don't know that anywhere as equivalently remote exists post Eisenhower, in the lower 48 it is not possible to be more than 27 miles from a maintained paved road. We've radically changed the physical environment.