One grainy video of Bigfoot here in the NW spawned a movement, and $$$ and folklore.
Perhaps the movement got so big that Sasquatch fled to Afghanistan?
The creatures are documented all over the world hundreds of years before the Patterson film. But they will be doubted until someone drags a dead one to the coroner's office, or captures and exhibits a live one.
A book from the 1970s, "Abominable Snowmen- Legend Come to Life" by Ivan T. Sanderson is an excellent read on them.
They have been talking about the Yeti for centuries. Bigfoot is a mere youth in comparison.