This a personal theory and not a conspiracy theory as such. The legends of Bigfoot go all the way back to time immemorial.
Every culture on Earth has legends of Bigfoot, whether they called it Sasquatch, Skunk ape, Yeti, Yahoo, the Abominable Snowman or any of many other monikers. The case of the Yeti has been solved. I don’t have the story in front of me so I will paraphrase. I man was mountain climbing in the Himalayas approximately 20-30 years ago. He was confronted by a large creature that he could not identify. It charged and he shot and killed it.
He camped for another two days at the site due to weather until another mountain climber came along and he told his tale and show the man the body of the creature. Again it could not be identified. The man who had shot it took a clipping of hair form the body and kept it for over ten years until something motivated him to take it to an Anthropologist.
The Anthropologist took a DNA sequence of the hair and could not identify it, then he had an idea. He went to the museums of the world and took samples of extinct animals. An extinct polar bear was a match. So, the Yeti was very real. The Legends were true. There was a large mammal in the Himalayas that was unknown to us. There have been many other fish, birds, animals, insects and reptiles thought to be extinct which have been found alive and well. A professor once explained to me that the “tree of humanity” is not a straight line but rather a bush and that there have been many, many different kinds of “people” in the past.
The American Indians had many names for them but one translated to “The Ancient Ones”. Daniel Boone said that he was attacked by a ten foot tall hairy man in the woods of Kentucky and shot and killed it/him. Perhaps one of our long lost relatives survives to this day. The archaeological record is shallow and full of holes. Don’t be surprised if Bigfoot is found one day alive and well.