A few years ago I put a long, thick 100% wool sock in my compost bin to see if it would break down. A couple of years later it was still almost perfect - just the original hole in the heel!
I did exactly the same. It was perfect for years. In the end I pulled it out of the compost, concluding that it was mis-sold and must contain polyester or some such. The weave hadn’t even started to break. I have put wool fleece in the compost before now, and cotton t shirts. And it all ends up disappearing, but not the sock!
Were the non-rotting wool socks machine-washable? If so it's probably the processing to make it not shrink or felt that's also made it not rot. See here (it's about knitting wool but I guess it's the same or similar for wool made into garments) https://mountainmeadowwool.com/blogs/the-mmw-blog/the-skinny-on-superwash-and-non-superwash-wool. In particular "To eliminate felting, the superwash process involves exposing the fiber
to a chlorine gas that erodes the scales. After the scales are removed
the wool is then coated with a plastic to fill in the places where the
scales were removed."
Doncaster, South Yorkshire. Soil type: sandy, well-drained
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