One should be wary of going to Campbell for anything historical. He was trained in psychology and drew what he knew about cultural comparisons from Jung, also a psychologist with only speculative understanding of the past. Both are noted for broad generalizations based on cherry-picked examples. For that matter, many folklorists find Campbell wanting when it comes to comparative research and analysis.

I know of no good evidence that cultural assumptions about the genders of the sun and moon represent a historical process. Some cultures assume the sun is male and some assume it is female; often the moon appears as just the opposite. It appears that the idea of a female sun was widespread in Northern Europe - in English one still speaks of the Man in the Moon. I suspect that the female sun was displaced by more recent acknowledgement of the Classical Greek understanding of a male sun - but I am not prepared to say that this was, in fact, a recent historical process or when this occurred.

The crucial thing to understand is that there is no evidence of some sort of widespread prehistoric supplanting of a female sun by a male one. It is simple a matter of cultural assumption not generally tied to history. Dismissing the Japanese female sun as some sort of relic from prehistory is typical of the Jungian/Campbell molding of the facts to suit the theory. As is typical, Campbell speculates on something no one can know, and then passes it off as part of his professed remarkable understanding of humanity, history, and cultures in general.