How about THOUSANDS of people keeping it all a secret?
This is putin trying to create and issue.
Truly not a problem.
1. Compartmentalization means most don't know. All they know abut is the part they worked on. Then they'd get the final motion picture show everyone else gets.
2. Where it's actually necessary to let people know, you have three immediately applicable levels of insurance.
The first is loyalty pre-screening to the level of a general top-secret clearance.
The second is simply a threat. On the mild side, the threat could be loss of pension, medical care, salary, employment. After that, well, how high do you want to go? Everyone has families and wants to stay alive and not be considered crazy. Bummer if anything happened to those things.
Third, though, is to have a good cover story. What if the whole fraud was explained as the cover for something else, something really dangerous in some way that threatened America? What if the moon landing fraud was explained as a way to deal with this other thing, this other issue, while saving millions of American lives. What then? People would shut up on their own, that's what - and be proud to do so. What kind of cover story? LOL, anything! Aliens, top secret technology development that has to be done openly, psyops in the cold war, distraction from Viet Nam. There are entire divisions of intelligence agencies that do nothing but come up with cover stories. Simply not a problem. And if it was something real (because the best lie is a misapplied truth), then other countries would go along with it for their own best interests as well.