We have found the skeletons, and we call them Gigantopithecus, not Bigfoot :)

https://en.wikipedia.org/wiki/Gigantopithecus

So we know for sure really huge apes, possibly as tall as 3 meters for sure used to exist. I'm not saying they still do, they probably don't. But it's not as big of mental hurdle dor me to clear, to consider if they have lasted, than for example, to believe in flying saucers from other solar systems.