We used to make them in the alfalfa fields back in 1956 New Mexico. That is, until the owner complained to dad.
Nothing mysterious about them.
I still think the best comment on crop circles was by the man and woman from rural England, who said, in extremely rustic accents: “We think they’re extraterrestrials.”
They could have been caused by a very large dog getting ready to go to the bathroom.
The article within that link, “One Woman’s Arduous Journey, etc” is really mind-blowing, when you see the complexity of the designs she has photographed in England, assuming they are verifiable. Not just your granddad’s circles — these are like precise digital images in a variety of patterns.