system
A chat on 4chan
human
Facts:
Camera was on loan to film a movie about Bigfoot.
Instead of leaving it at camp, Patterson was riding around with this expensive, loaned camera in his saddle bag.

If he was going to film a movie about Bigfoot, that implies they had a Bigfoot costume pre-made, which Patterson has NEVER mentioned.

Brother in law doesn't remember where he had the film developed. There was only 1 place capable of developing this type of film within 200 miles that was open on the weekend (when he claimed he had it developed) and they did not do it.

Patterson made a living on taking people out on bigfoot hunting tours.

They went back to the site to take molds of foot prints but did not measure the trees to verify the creatures height.

Even though they returned to the site themselves many times, once people asked to see the site themselves they could no longer locate it.

There's even more to the story but I'll hit character limit.
It's a hoax.
100% guaranteed.
gpt
Another fact: the location filmed is nearby Bluff Creek, it had been rediscovered. Also, the location was subjected to a flood, causing the area to look much different than it would've normally. The reason why it became difficult to find the exact location was because of the vegetation regrowing and taking over the area, making it seem completely different. Patterson and Gimlin weren't wealthy. I don't know how much of a living you can get from a 'bigfoot hunting tour', but I can't imagine that it'll be much. To construct a costume to match the detail in the video would've been expensive and outright impossible in 1967, given the technology and effects at the time.