The Moon Hoax Theory Claims:
A certain number of people within the Apollo Mission were aware of the hoax and managed to keep it secret. Different variations of the theory offer different scenarios regarding who was involved.
How many people would have been needed to stage a successful moon landing hoax? There are three possible scenarios:
Let's look at each possibility...
(1) Only a handful of top-level administrators knew about the hoax.
This scenario is attractive because it offers the best chance of maintaining secrecy. If only a very small number of people are involved, it is plausible that the hoax would never be revealed.
Unfortunately, these senior administrators would have no practical way to implement the hoax. Even a fake moon landing needs engineers, set builders, film producers, actors, etc. Clearly this scenario does not work.
(2) A number of carefully chosen people knew about the hoax, but most employees did not.
This scenario offers a compromise by including personnel on a "need to know" basis. The assumption is that NASA employed enough staff to stage the hoax, while the bulk of the Apollo contractors genuinely believed they were working towards a real moon landing.
This is where some knowledge of the project's scale is important. The Apollo mission required a large number of inter-related projects to succeed. For example, a company called Grumman was responsible for designing and building a lunar lander. Not only did the lander have to work independently, it had to work in conjunction with the command module (designed and built by North American). There were many such companies involved, each contributing some integral part to the whole mission.
The critical point is that these companies were designing the components - they were not simply assembling them to someone else's specifications. Remember that these components were effectively new inventions. Each company was tasked with inventing new technology, constructing it and proving that it could work with other mission components.
If any particular particular component didn't work, scores of engineers at different companies would have known.
In fact, the number of people in the "need to know" loop includes virtually every single engineer directly involved in development. This brings us to the final possibility...
(3) Everyone directly involved in the Apollo missions knew about the hoax.
Thousands of administrators, engineers and support staff were directly involved in developing the lunar landing technology. Under this scenario the chance of maintaining secrecy is effectively zero percent.
Strike three - all scenarios are out. There is simply no plausible way to execute a hoax of this magnitude.