In cinema, a making-of or behind-the-scenes is a documentary featuring the production of a film. It describes how the scenes in a movie were created. Some trolls took footage from the behind-the-scenes of various space movies and present them to flat-Earthers as though it is how space agencies “faked” their videos.
Flat-Earthers fail to realize that these footage were just behind-the-scenes of space movies and unrelated to the actual space footage from space agencies. These spread as hoaxes in flat-Earth circles.