The contractors and subcontractors all did their jobs to the best of their ability.
They had no special insight on whether the landings were real or fake.
NASA had simulation after simulation after simulation....for the vast majority of their employees they had no way to tell a simulation from the real thing.
That was not their fault either.
This was 1969. No such level of sophistication existed to be able to fake such a complex event to all those workers.