Actually explaining how it got to the Seven Site is irrelevent because as yet no one has satisfactorily shown that the material at the Seven Site has any relationship to events occurring in 1937, or whether the unknown castaway, for that is what they actually are, even had any contact with the shoe.
I think you mean to say that, as yet, no one has shown to Dan Kelly's satisfaction that the material at the Seven Site has any relationship to events occurring in 1937.
As for Gallagher's identification as Mr Lanz pointed out what evidence do we have to suggest that he simply didn't mistake a small male shoe for a woman's shoe.
The evidence we have to suggest that he simply didn't mistake a small male shoe for a woman's shoe is his clearly stated estimate that it was a size typical of a man's shoe.
The big puzzle as discussed here so often and in so many different threads still remains what is the relevance of the Seven Site and its material to either Earhart or Noonan.
For starters:
Earhart and Noonan disappeared in 1937.
The bones and campsite of what appears to have been a female castaway were found in 1940.
Parts of a man's shoe and part of a woman's shoe were reportedly found with the bones.
The conclusions Gallagher drew from the part of a woman's shoe are explainable if the sole he found was from a shoe AE is known to have had with her.
A sextant box found with the bones had numbers on it that strongly suggest that it was the same kind of sextant used by Noonan as a "preventer."
TIGHAR has recovered numerous artifacts from the site that seem to speak of an American woman of the 1930s.
That now that the sole has been ruled out still remains the central issue.
Who ruled out what sole? The dark rubber sole TIGHAR found was on the opposite side of the island from the Seven Site and has nothing to do with the sole Gallagher found.