How or why did judaism evolve?

Answer 1

Judaism has had to adapt to not having the Great Temple in Jerusalem and to being mostly in countries where Judaism was not the majority religion. As a result, a number of rules specifically dealing with the Great Temple are no longer followed. Additionally, the Rabbis wanted to protect the observance of the Torah Laws by creating additional, more restrictive laws to prevent unintentional breaking of the Torah Laws.

Finally, there was also the recent development of Liberal Judaism, which represents a fundamental shift in Jewish observance and belief. Using modern, and non-Jewish ideas to influence the way in which Judaism should develop.