Exactly, so why would the Alexandrian Jews include extra books in the Septuagint, and why would the same collection of scripture be widely used in Palestina as well (something like 80% of quotations in the New Testament are from the Septuagint).
In my mind, it could only be because the actual canon was unsettled among Jews at large. The Jerusalem leadership may have believed it to be settled, but that does not really speak to the popular practice of the religion, does it? The New Testament shows a number of competing Jewish groups with differing power bases and even differing beliefs on matters such as the resurrection.
Because they were forced to.
The translation of the Torah into Greek caused irreparable damage.The Torah was given to us in one language and one language only. The nuances, subtleties, and implications of the specific words chosen are lost in translation. The "70 facets of Torah" which our Sages wrote about can't readily be seen or gleaned from a translation.
In addition, when one translates, one is forced to chose a specific interpretation that he or she feels best express the meaning of the original words. Alternate meanings or interpretations are discarded. It was this aspect of the translation of the Torah that was most harmful. It gave license for people to begin explaining the Torah as they saw fit, ignoring other relevant and applicable meanings that came from Sinai as well.
The teachings of the Sages were disregarded, and the holy words of the Torah were corrupted. For this reason, a fast was warranted.
- R. Yehudah Prero