Where did the Jesus myth come from?

[Epimethean]

I have read that passage. I don't think he is suggesting that he didn't understand it. It is phrased rhetorically, and the pivotal term is "manly," which hits back at the point he made just before with the reference to a key point, which is the shift from Mother Right to manly might.

Here is Campbell elaborating on that issue:

Toward the end of close of the Age of Bronze and, more strongly, with the dawn of the Age of Iron (c. 1250 B.C. in the Levant), the old cosmology and mythologies of the goddess mother were radically transformed, reinterpreted, and in large measure even suppressed, by those suddenly intrusive patriarchal warrior tribesmen whose traditions have come down to us chiefly in the Old and New Testaments and in the myths of Greece. Two extensive geographical matrices were the source lands of these insurgent warrior waves: For the Semites, the Syro-Arabian deserts, where, as ranging nomads, the herded sheep and goats and later mastered the camel; and for the Hellenic-Aryan stems, the broad plains of Europe and south Russia, where they had grazed their herds of cattle and early mastered the horse. 1

and,

For it is now perfectly clear that before the violent entry of the late Bronze and early Iron Age nomadic Aryan cattle-herders from the north and Semitic sheep-and-goat-herders from the south into the old cult sites of the ancient world, there had prevailed in that world an essentially organic, vegetal, non-heroic view of the nature and necessities of life that was completely repugnant to those lion hearts for whom not the patient toil of earth but the battle spear and its plunder were the source of both wealth and joy. In the older mother myths and rites the light and darker aspects of the mixed thing that is life had been honored equally and together, whereas in the later, male-oriented, patriarchal myths, all that is good and noble was attributed to the new, heroic master gods, leaving to the native nature powers the character only of darkness--to which, also, a negative moral judgment now was added. For, as a great body of evidence shows, the social as well as mythic orders of the two contrasting ways of life were opposed. Where the goddess had been venerated as the giver and supporter of life as well as consumer of the dead, women as her representatives had been accorded a paramount position in society as well as in cult. Such an order of female-dominated social and cultic custom is termed, in a broad and general way, the order of Mother Right. And opposed to such without quarter, is the order of the Patriarchy, with an ardor of righteous eloquence and a fury of fire and sword. 2

The Masks of God-Occidental Mythology

1. pg 7
2. pg 21

Further, Campbell does reference the Mother as representing "Space, Time and Matter," which is fairly concrete reference to the cosmic myth. The shift as male dominance enters the picture is fully discussed, and I do not see Campbell allowing as to a failing to understand here, but rather, that the change is not completely natural.