My personal favourite is that they did indeed land on the moon, and filmed it, but the footage got ruined on re-entry, and thus has to reproduce it in a studio as 'proof'.
And as for Virgil I. Grissom, Edward H. White and Roger B. Chaffee — three astronauts who died in a fire while testing equipment for the first moon mission? They were executed by the U.S. government, which feared they were about to disclose the truth.1 billion percent it happened. I am no US Government fan but can you imagine how many people would be involved to hoax it? We are talking thousands of you human creatures, the money one could make to leak their story.
...the footage got ruined on re-entry, and thus has to reproduce it in a studio as 'proof'.