If we delve deeper, we will see that Haman’s decree actually stirred the singular quality, the segula, of the Jewish people. The decree made it clear that the Jewish people were willing to make great sacrifices in order to hold onto their faith. After all, they could have assimilated among the gentiles and saved themselves from annihilation. Nevertheless, they did not try to escape their Jewish destiny. On the contrary, the decree inspired them to repent and strengthen their faith and commitment to the Torah and the mitzvot.
The events of Purim were so momentous that the Sages stated that Israel accepted the Torah anew at the time of Aĥashverosh. In a certain sense, their renewed commitment at that time was greater than their original acceptance of the Torah on Mount Sinai. When the Torah was first given, Israel was forced to accept it, as it says, “They took their places at the foot of the mountain” (Shemot 19:17). The Sages comment (Shabbat 88a):
This teaches that the Holy One, blessed be He, overturned the mountain upon them like a cask, and said to them, “If you accept the Torah – good; if not – here shall be your burial.” R. Aĥa b. Yaakov said, “This furnishes a strong protest against the Torah” (since they accepted the Torah under duress, they are not obligated to uphold it). Rava said, “Even so, they re-accepted it at the time of Aĥashverosh, as it says, ‘The Jews upheld and accepted upon themselves” (Esther 9:27) – that is, they confirmed what they had accepted long before.”
Many commentators explain that God “overturned the mountain upon them like a cask” in a symbolic, spiritual sense. After all the great miracles of the Exodus from Egypt, the splitting of the sea, and the awesome revelations at Mount Sinai, it was impossible for the Jews not to accept the Torah. However, the question still remained: Would the Jews stay connected to God and His Torah even afterward, when they become detached from those miracles and wonders? Indeed, there were ups and downs, until the events of Purim took place. That is when it became clear that the people of Israel’s connection to their faith and to the Torah were absolute. The terrible decree made it clear that the price of belief might be unbearable, but the Jews still chose to adhere to their faith, repent, and pray to God, without any coercion. Not only did they return to observe the 613 mitzvot, they even instituted additional mitzvot after they were saved: the mitzvot of Purim.
Thus, we were privileged to build the Second Temple, and a door was opened for the advancement of the study of the Oral Torah, which was the main spiritual enterprise of the Second Temple era.