IIRC, the makers of that film eventually admitted the film was a hoax, but no one remembers that admission. Just like when people admitted making the crop circles, but other people keep going with the theory that aliens made them.
http://findarticles.com/p/articles/m...28/ai_n6145280
After nearly forty years of secrecy, the truth behind the world-famous Roger Patterson Bigfoot film has been revealed. The man who actually wore the costume and played the role of Bigfoot in the film has been located and has made a full confession. Moreover, the husband and wife team who made and sold the Bigfoot costume that Patterson used to fake his movie have also confessed, and several other important eyewitnesses have come forth with corroborating evidence. In a new book, The Making of Bigfoot: The Inside Story (Prometheus Books, 2004), Seattle-based author Greg Long reveals details of the hoax, the result of a six-year investigation which also clandestinely involved author Kal Korff.