Before Ezra and Nehemiah there was no "Jewish" religion. The Levites were the priests over all of Israel. The Levites remained with Judah when God divided Israel into two kingdoms. Jeroboam set up illegitimate priests, but the people still knew of the prophesied messiah, and when Jesus arrived on the scene, they knew immediately who he was. Some Jewish rabbis also knew. While the Jews kept the Law they corrupted the meaning of the high days by inventing 'traditions', removing any suggestion of a suffering messiah.
Regarding 'original sin', God allowed Eve and Adam access to the fruit of the tree of knowledge of good and evil. Doing so God also allowed Satan to influence mankind, however he withheld his Holy Spirit from mankind until the death of Jesus and the founding of the church. So, with the free will of deciding what is good and what is evil, coupled with the influence of Satan, mankind has tended towards evil from the beginning. And while goodness is also intrinsic in man, as a necessary survival device, evil still prevails.