Not true.
Ever heard of that thing called "The Manhattan Project"?
Tons of people working on something totally top secret. Nobody knew everything. Just enough to do their job.
They had nothing specific to tell anyone?
The Manhattan Project was a HUGE conspiracy project. There were entire towns of people working on it.
That was also done way the heck before the internet/blogosphere... The press stifled the fact that the President of the United States was gravely ill and could barely move. Also stifled news of the First Lady having a lesbian side relationship. All this around the same time of the Manhattan Project. Things like this would be exposed today much more easily.