Because of theological supersessionism, ie. the idea that Christianity was the proper heir to the Jewish tradition, and that Jews had broken that link with the past. Judaism was thus seen as an ossified, antique faith which had not been subsumed into Christianity because of stubbornness, to the point that, starting in the 12th c., some Christian writers who read rabbinic texts declared contemporary Jews "heretical" because the religion could not have evolved from its antique form.

Additionally, Christian kings comparing themselves to biblical rulers is a tradition far older than the Tudors. Among others, it was a defining sign of Merovingian authority, and also why rulers were (and are) typically depicted with scrolls which represent the Law of the Old Testament, while ecclesiastical figures carry a codex representing the New.