It all depends from where we look at it !
SYNCRETISM -
From an Anthropological point of view, all myths & religions we can study today are syncretic.
The severe persistent climate changes of the VII-VI millenium BCE made winners & losers among the Gods of many Cultures & People, who were fleeing long floods & droughts, and moved around on long distances, encountering other Cultures. Some of our myths & legends goes back to these ancient times; stories which were incorporated into successive narratives.
With respect to the Judeo-Christians, there is plenty of syncretic material to work on : Sumer, Babylon, Zoroaster, Ugarit, Egypt, …
Our first five books (the ones which are not attributed to a specific writer) certainly are an aggregate of a variety of sources spread on many centuries, coming from varied geographical areas. An aggregate creates the kind of questions for which we need to build a lot of logical artefacts, in order to try to strengthen a specific explanation/ interpretation which links it all. As a consequence, many different viewpoints will pop-up.
In these old days, the Law was the one of the religion. Within the new Persian Province, the Israelites had no unity of ‘’Law’’ (unity of Law is convenient for the persian king, in order to manage the province). We ought to remember that we are lucky that the Persian King decided to get Hesdras, one of his reliable Israelite Civil Servant, to put together in a single Book what will become the Law of his newly acquired persian province.
MONOTHEISM -
The Bible tells us that the Ancient Hebrew were polytheists. (Jeremy 2:28) (Genesis 6:2) (2 Kings 23:5) (Psalms 95:3) (1 Kings 11:33) (Juges 2:13) (Psalme 82:1) (Isaie 1:3) (Jeremy 32:35) …
Even King Solomon has constructed an important place for the God Moloch. The cult of Moloch is well known for its rituals of holocaust of children.
Also, archeology confirms : many varied idols were venerated. In Egypt, the Israelites venerated also the Egyptian God of Water, alongside the local ‘’Astarte’’. That was in the V century BCE, if I remember well. But Baal was also venerated alongside other Gods/ Godesses in many places.
The idea of monotheism came progressively, during/ after the Exile, where the fame of Zoroaster was growing. And particularly with the Persian King Cyrus-the-Great who acted consistently with Zoroaster’s teachings.
THE SAVIOR -
The Savior ‘’story’’ clearly comes from the older part of the Avesta: the Sacred Book of Zoroastrian monotheism (I am not talking of the polytheist Magi which used opportunist Syncretism : Mazdean polytheism + cult of Mithra + their divination speciality).
The difference between Zoroaster and the Judeo-Christians is that Zoroaster displays a completely logical eschatology : from spiritual creation, reasons why God created the physical world (in 6 steps), the Free Will, the Covenant, the post-mortem rewards & sufferings, the Paradise/ Purgatory/ Hell, The Signs of the End of Times, the Savior, the Resurection, the Apocalypse, The Kingdom of God.
It appears clearly to me that the links between the different elements of the Christian eschatology sounds more like a syncretic aggregate of elements, a kind of patchwork. The zoroastrian eschatology, instead, looks more like a puzzle, where each element has a logical reason to be where and how it is.)
