Bigfoot was real but was has been almost certainly been driven extinct.
Most likely it was quietly exterminated at the behest of companies engaged in logging, mining, etc to avoid attracting attention and disrupting business, as is being done to native species and human populations right now in other parts of the world like the Amazon. Just like was done with many species in North America. It's not anything supernatural; it was almost certainly a branch of archaic hominin that crossed Beringia during one of the many glacial periods in the last few million years. Other hominin species are already known to have reached northeast Asia, including Homo erectus despite being archaic by Homo standards. Evidence for australopithecines in east Asia is fragmentary and less conclusive.
However, any numbers of bigfoot were probably already small by modern times. Based on all reports they were easily large enough to have been affected by the megafaua mass exctinction in North America 13000 years BP. It's likely they were already endangered by the time white settlers started arriving, and possibly when Clovis people arrived across Beringia during the last glacial maximum. Given the differences to modern humans, they would likely be easy prey, for either group. This wouldn't be the only example of a population of ice age megafauna surviving later than most of their ancestors. An insular population of wooly mammoths survived on Wrangel Island in siberia until 4000 years before present.
Bigfoot's appearance and evidence profile is additionally consistent with more recent findings in early human evolution. At the time the most famous bigfoot evidence, the Patterson-Gimlin film, was recorded, it was widely believed that humans evolved "brain first," with tool use evolving secondarily to support the brain, and bipedalism evolving secondary to both. A bipedal ape with otherwise archaic features was relatively unfamiliar back then. Later evidence, especially into the 21st century, has shown that early Australopithecines commonly had similar morphology to bigfoot: well developed bipedalism but otherwise archaic features, including the barrel chest, long arms, and small cranium similar to other great apes.
The presence of one or more other hominin species in the Americas prior to the Clovis migration could also explain the evidence of prior human habitation. There are a few cases of evidence for human presence further in the past than the last glacial maximum, most prominently the footprints in White Sands, New Mexico. There is, however, no evidence of stone tool use. That could just be an aberration since there is so little evidence in general, but otherwise artifacts of tools are pretty much ubiquitous as evidence of human presence, going back before the evolution of the genus Homo. If further evidence appears of human habitation in the Americas without evidence of stone tools, that would strongly suggest it was some other branch that arrived in the Americas pre-Clovis.
Further, genetic evidence shows no sign of any other homo sapiens population in the pre-Columbian Americas apart from the (relatively small) group that arrived at the time of the Clovis people. If there were hominins in the Americas before that time (which seems all but proven), they must have not bred with the humans who arrived later. This could be due to dying out before then, neither group trying to interbreed, or biological incompatibility. Given that there is at least some trace of the other known Homo species in modern populations, that suggests it's more likely that whatever hominin pre-dates Clovis was too distantly related to the Clovis people to produce viable offspring, if their presence on the continent ever overlapped. This further points toward an early arrival of another hominin offshoot.
Bigfoot was likely a small population of australopithecines that barely survived into modernity after spreading into the Americas in the distant past. One of the closest resembling groups would the the contested Paranthropus genus, AKA the robust australopithecines. There is possible evidence for their presence in China, and they share the prominent sagittal crest that bigfoot appears to have (distinguishing them from most other hominins). The biggest discrepancy is the much larger size and heavier build of bigfoot, but other non-hominin apes have evolved to be even bigger (modern gorillas and extinct gigantopithecus), and prior to the megafauna extinction 13000 years ago the continent readily supported very large mammals. The Pacific northwest where bigfoot is purported to have lived continues to support mammalian megafauna (moose and bears, i.e. herbivores and carnivores).
BiKKKfoot is a fascist.