Someone took a bush hog, turned it upside down, welded a steel drum to it with some drain holes and a collar that slipped up or down to block them. Hooked up to a tractor it spun the drum around; they used the higher PTO speed and lifted the collar for the drain cycle.

I'm sure rednecks have been making washing machines on similar principles since steam engines.

Also, it exists. The people who will go from having to slap clothes on rocks to this wouldn't be as quick to shout "meh, it's been done before"