When you have to scratch and you are a 2,000 pound bison bull, what are you to do? Roll in the dirt! 😉 That much weight rolling in dry dirt definitely creates a cloud of dust as you can see.
This big boy is one of the largest in the herd, something you can easily see, and judging from those horns, he has been battle tested many times.
Called wallowing, bison may do this for a few reasons. It helps them shed fur, gets rid of flies and, during mating season, serves as display of dominance.