It's not a question of believing anything but the photos, which only could have been taken on the actual Moon.  The people who tout this inane idea of faked Moon landings don't even have a theory.  Mostly, they do not understand photography.  Nor vacuum.  Nor low gravity.  Nor rocket propulsion physics.  Nor anything they ignorantly put forward as an objection.  Sheer ignorance, refusing to learn, and blaming everyone else for their own inability to understand. Yes, I'm on a rant.  I'm a 40-year veteran of the space and defense industry, working in the problem area and this degree of knuckle-headed stupidity gets my goat.