What they often don't show us is how many bikes they crashed to get to that point. They often train with a combination of over or under inflated tires, use huge rear sprockets and other mods that may not be that obvious like head angle changes and fork length, etc. One stunt rider that does show a lot of this info on YT is Jorian Ponomareff, but you'll have to sit through much of his sometimes cheesy humor, ..and it's in French.
RE: Sumo stunter Arttu Stenberg