I do have a theory...
Long ago, many PNW indiginous people tribes were very short. So, when they saw a 6 foot 5 fat Russian fur trader that was drunk, smelled bad, acting crazy, wearing fur, extremely hairy...they immediately started telling stories about BIGFOOT.
Here in the PNW, dirt bike circles, we also have a local legend... Blood Rock.
A number of videos about this place, where natives made human sacrifices...
https://www.youtube.com/watch?v=OjaR0cIU1Kw