The Romans suffered repeated revolts in Palestine lead by people claiming to be the Messiah. Herod was appointed king of the Jews by the Romans. Herod had no legitimate connection to King David or the line of Jewish kings who were descended from David. In fact, many, if not most, Jews did not consider him Jewish. Perhaps the simplest way to explain Herod's ethnic background quickly to the modern reader is to say he was an Edomite, a group that claimed decent from Jacob's twin brother Esau. Because Herod's claim on the Jewish crown was so weak, anyone claiming to be the Messiah and descent from David was in effect questioning his appointment as king, and therefore the rule of the Romans who made the appointment. So Luke naturally did not want to write anything that would lead the Romans to think Jesus was a political king when writing to a Roman official.
Luke could not deny that Jesus was somehow the descendant of David. That was simply too important to the Christian faith. The word Christ is Greek for Messiah, and the Messiah had to be the descendent of David. But Luke did shift the emphasis in several ways.
First, Luke's genealogy goes from David through Nathan rather than King Solomon. Nathan was never King. Matthew on the other hand traces the genealogy from David, to Solomon, and down through a series of other Jewish kings. In Luke's genealogy there is only one King. In Matthew's genealogy there is a series of fifteen Jewish Kings. This is one reason Matthew's genealogy represents a much stronger challenge to Herod and therefore the Romans.
Note also that in Luke's genealogy Jesus has a whole line of male ancestors who were not Kings of Judah during a long period in which Judah had kings. This would greatly weaken any claim that Jesus should be a political king.
It also has been noted that the genealogy of Luke has many more links in the final half millennium before Christ. The Catholic Encyclopedia notes that St Matthew has only nine generations between Zorobabel and St. Joseph. This is a period of 530 years. Luke on the other hand has eighteen. The Catholic Encyclopedia makes the point that Luke's list is more in line with the normal course of events, as Matthew's list assumes the average generation is fifty years long. If you wish to check out The Catholic Encyclopedia's article on the genealogy of Christ here is the link. My point, however, is that the greater number of links given by Luke made any idea that Jesus was the rightful king in the traditional sense even more tenuous. He was still of the house of David and legitimately the spiritual Messiah and founder of Christianity, but not a political king that should worry the Romans.
Luke further de-emphasizes the connection between Jesus and David by placing the genealogy after his story of the nativity and early life of Jesus and at the beginning of his public ministry. When one is addressing a powerful figure it is common to start your speech off with less upsetting news before mentioning difficult topics. This seems to be what Luke is doing. Matthew who is addressing a very different audience placed his genealogy first.
If we look at the differences between the nativity stories of Matthew and Luke we can see the same influences. Luke carefully avoids discussing the death of the Holy Innocents, as one naturally would if one was writing to a Roman official. Once again Herod was a Roman appointee so this was indirectly a Roman crime.
Luke emphasizes women and old men past military age in his nativity story. He also brings in the politically unimportant shepherds, and leaves out the wise men. Part of his message seems to be that Christianity is not threatening to the Roman Empire.
I have a much more extensive treatment of the differences between the Matthew's and Luke's nativity stories here.
Tell me what you think. Furthermore, if there are any researchers in the relevant areas who wish to work with me on publishing these ideas please contact me. My field is economics so I am not an expert in publishing in this area. Here is my contact information..
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