One thing you seem to be completely unaware of is the compartmentalized nature of information, and how certain secrets are treated as the "holy of holies" which only a select few will ever be allowed to see the workings of.
All that would mean is that bits and pieces would have leaked out until enough was gathered that you could see the whole picture. We know from history that it is just impossible for something that big to remain completely secret.
But that is the point - bits and pieces have "leaked out", or rather bits and pieces are noticebly fraudulent.
If you watch the majority of the "onboard the ISS" videos with a critical eye, you'll notice there is something severely wrong with the way the astronauts move and change direction as though inertia was not a factor in their movement. Even in free-fall weightlessness a 80kg person still has 80kg of mass. Moving, turning, slowing, stopping would all take considerable exertion, yet the astronauts do it with without effort. Makes no sense in the context of a truly weightless environment, but makes lots of sense if they are simply in a green-screen room suspended by harnesses with most of the motion occuring with the camera and post-production editing instead of the (actor) actually reorienting himself.
The public at large unfortunately does not have an intuitive grasp of momentum and how it works, so feeble special effects is all it takes to fool them. Most of the time they don't even bother to use the simulated weightlessness of a "vomit comet". Composite video is far easier and has the added bonus of being able to have long sequences without edits, whereas the vomit comets only get around 30 seconds or so of time for weightless acrobatics.
I wouldn't quite call it a leak if the only place that information gets disseminated to is an obscure website that no one really visits, and of those that do, most don't take seriously. I'm talking we would have something in larger circles with a clear whistleblowers and some documented evidence. Snowden is the most common name known about our spying issues here but he was far from the first NSA whistleblower.
Also, you do realize that weightlessness means just that right? It would take as much effort to move there as it does for you move a feather here so it looks like fundamental understanding is flawed so you see issues where none exist. If anything, if they were faking it I would expect to see more force needed, like say, if you were pushing through water and not in space. With no one being in any kind of scuba gear then I would wonder how they would only appearing to be weightless for so long. Video editing can do a lot for sure, but it can only do so much.