I very much welcome this initiative of yours to discuss the book "Caesar´s Messiah" in some detail. It is certainly a groundbreaking work that deserves serious study.
Thanks for pointing out the importance of the Esther and Mordecai story. Perhaps the author deliberately choose this particular narrative as a biblical example of typology since it fits so well the theme of the book.
I have to defend the author of the book regarding the historical existence or non-existence of the Jesus of the gospels. There certainly has been found NO ARCHAEOLOGICAL EVIDENCE for the existence of the Jesus of the four gospels! Some member of the Herodian family may very well have been pushed on the people as the promised Messiah, as you say, and the Gospel Jesus may to some degree have been patterned on the life of such a person. BUT: the four gospels are pieces of literature. And thus the Jesus they proclaim is (of course) a literary figure, a fictive hero. This fact must be fully realized.
There may be archaeological finds related to some Herodian prince of that time but certainly there are no archaeological finds related to the fictive Savior and Son of God! You may as well go looking for archaeological evidence for the existence of Pooh Bear or Sinderella.
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