[wl]

Cyrus was the Messiah, too, but nobody pretends he was descended from King David. In any case, Jesus fails most of the Messianic criteria of Second Temple Judaism. Early Christians had to significantly revise their concept of Messiah to get Jesus to fit. Indeed, the NT makes light of the fact that Jesus was not the Messiah the Jews were expecting, although it implies they were wrong.

In any case, the basis of Christianity is that Jesus was God incarnate, died for the sins of the world, rose from the dead, and will come again to judge the living and the dead. Some early Christian polemic about interpretation of then-centries-old prophesy isn't core to that. It's a problem for fundamentalism, but that's an entirely separate issue.