I understand that Christians, especially Catholics, have an alternative to the Jewish history. I’ll just point out that Jewish scholars disagree. Two different religions, after all.
Besides, the real fight is between Protestants and Catholics, who do not agree on canon and claim to be the same religion.
If we stand apart from ideological perspectives and examine the historical evidence, it becomes pretty clear that the whole concept of a canon was unknown until a conflict arose on a larger scale between Jews who were Christians, Jews who were not Christians and the large mass of monotheistic Gentiles who became an important part of that field of conflict.
That's when Christians began insisting on the value of the Septuagint and Perushim became enemies of the Septuagint.