There may be a natural explanation for basic circles but the modern trend for expansive fractal forms is pure human vandalism.
The trampled crop is not going to recover and that spoiled area will make the surrounding crop liable to contamination when harvesting - from soil, weed growth and other damage left by visitors.
Some of these over-sized variants appear to cover several acres.
A crop of wheat will cost up to £300 acre to establish, and the grain from that area might be worth £1000 which could be all or part lost.
The crop they are trampling into dirt is typically wheat and potentially destined for human consumption so these issues are not trivial.
I don't like to see drones being used to publicise the vandalism and fake pseudo religious piffle.