We seem to collide head on here, since my premise is somewhat the opposite of yours! I think that history has a mythic basis. Or to be more correct, I think there´s a cyclic repetition: myth - real life - myth - real life, and so on. One always influencing the other.
So, in a way - as always, perhaps - we´re both right. You pick a myth and spy an historical background to it. I pick a piece of history and find a myth behind it.
The ageold myths like to put on new garments from time to time. However, at the core there´s always the same old story - which is "written in the stars". Thus, for example, the legends of King Arthur represent the ancient Sun myth in a but another garment.
I fully agree with you that the Bible is all myth - although dressed up to pose as an historical record. You see, as always the old myth or star lore takes on certain new garments. But the biblical garments barely suffice to slightly veil the mythic core.
You ask why I advocate keeping a possible real person Jesus "separate" from the mythic Jesus of the Gospels and the Church. Well, its just not to mix them all up. I think I´ve already answered that in my reply to Charles, at:
Best regards, Helge
© Charles N. Pope, US Library of Congress. All rights reserved.