I theorize that some of these astronauts never realized they were NOT in space. Perhaps a few of them were played just like the public.

They've could've faked an environment for them or maybe they learned the truth at some point on their missions. They already had simulators where astronauts practiced, I imagine they could use the same technology to make some astronauts believe they were actually in space.

Neil Armstrong certainly gives me that impression. He believed he was going to the moon and deserved to be a hero but got scammed and had to go along with it because of "national security". Buzz, on the other hand, his body language and use of words sound full of guilt and anger.

Alan Bell in this video gives me the impression that he firmly believed he walked on the moon. Which is a different story, I don't see how they could've faked that experience for them, yet again, they had a pretty huge budget and the burden of the Cold War on them, so who knows...