I stained this deck in June 2022. Before I touched it, it had never been stained before, but was considerably dirty. I thoroughly cleaned it with chemical cleaner, twice, and washed all of the cleaner off. I came back to it about a week later after a full week of sun and sanded the entire deck with an orbital palm sander. I swept and blew all of the dust off, and applied Behr semi-transparent deck stain using a paint/stain brush. The first picture is after I had finished. The second picture is after one winter (I'm located in Ontario, Canada).

The three things I think may be the culprit:
Was the wood not clean enough? Too much dirt left over?
Was the wood not dry enough? Too much moisture left in the wood?
Is Behr deck stain trash?

Before I redo it, I'm hoping to figure out why it didn't last one winter. I'd rather not sand it and re-stain it only for this to happen again next winter.

First image: https://imgur.com/a/hLXqGLo

Second image: https://imgur.com/a/ieDadI7