Up to that day, the Soviets had been so far ahead of us in space exploration that they would have easily discovered any flimflam. If so, they would have told the world right away and, given their record in space, the world would have believed them, not us.
The original Lunar Landing Hoax was started by some nutjob who was convinced that the Earth was flat, therefore impossible to orbit (for him, the whole space program, from any country, is faked).
The other original "contributor" was a journalist who was convinced that he had found the way to become instantly famous. His "logic" was easy: get an astronaut to swear ont he Bible that the trips were real, then sue that astronaut for blasphemy. Thereby "proving" the landings were faked.
This undermedicated journalist was, deservedly, punched in the mouth. When he tried to sue the astronaut who had punched him, he was laughed out of court.
This same journalist is still at it.
The recent versions, though, are just hoax for the sake of fooling people. Like Donald Trump who already knew that Obama's birth certificate was valid (it had been certified two years before the election by a court). However Trump also knew that if, in the USA, you say anything, you instantly get 20% of the people to believe you, regardless of how foolish the statement.