Chazal tell us (Shabbos 88a) that even after Matan Torah, if Bnei Yisrael would fail to comply with the mitzvos of the Torah, they could be exonerated due to a disclaimer: They had lacked a willful acceptance of the commandments since Hashem had held a mountain over their head thereby forcing them to accept the Torah. Tosafos explains that although they had already declared na'aseh v'nishma, they might have reneged on their acceptance after perceiving the tremendous fire that accompanied Matan Torah. The Gemara continues that nevertheless, they lost this excuse during the reign of Achashveirosh when they willingly reaccepted the Torah as a result of the great miracle performed for them.
How is it possible, asks Rav Wolbe (Daas Shlomo Geulah), that the generation of Mordechai was on a greater spiritual level than the generation that left Mitzrayim? After all, it is known that the Moshe's generation (the dor dei'ah) was the only generation in the course of all of history that was suited and spiritually capable of receiving the Torah at Har Sinai.
The answer lies in a close analysis of what occurred during Matan Torah. Hashem warned Moshe, "Set boundaries for the people around [Har Sinai], saying, 'Beware of ascending the mountain or touching its edge'" (Shemos 19:12). This warning was given once and repeated again just prior to the Aseres Hadibros. Additionally, the kohanim were warned not to rely upon their elevated status and try to ascend the mountain when hearing Hashem speaking to them. In other words, the natural reaction should have been that when Hashem revealed Himself to Bnei Yisrael, they would have instinctively rushed forward to try to get a closer "glimpse" of their Creator.
However, what actually unfolded was a different scenario altogether. As soon as they heard Hashem's voice, they quaked with fear and retreated nearly ten miles from Har Sinai. Moreover, Chazal tell us that they actually had to be revived since they died as a result of hearing Hashem speak. Consequently, they begged Moshe to act as an intermediary: he would hear the word of Hashem and relay it to the rest of Bnei Yisrael. Many years later, when Moshe castigated them, he referred back to this event and stated, "You weakened me [with your reaction]." He was distressed because he realized that they did not have the craving to connect to Hashem through love. Instead, their acceptance of the Torah was fueled by their fear of Hashem, and had the mountain not been held above their heads who knows if they would have accepted the Torah. Although their minds internalized the veracity of all they had heard, their hearts failed to internalize Hashem's word and merely followed the lead of the mind blindly.
We can appreciate Bnei Yisrael's behavior, because we also encounter similar feelings when we experience moments of spiritual elevation. Yom Kippur is a unique day which brings to extraordinary levels of loftiness, but who truly feels a desire to live on such a spiritual plateau all year long?
After experiencing the astounding miracle in the days of Achashveirosh, Bnei Yisrael's hearts matured and developed to the point that the heart did not have to blindly follow the mind's perception. The demonstration of Hashem's tremendous devotion toward Bnei Yisrael brought them to a whole new level of love of Hashem. They had no reserves about Hashem's commandments and they willingly accepted the Torah. Their spiritual level might not have been greater than that of their predecessors, but their hearts had been opened by Hashem's unique display of love for them. The Arizal said that in some aspects Yom Kippur is secondary to the day of Purim. Rav Wolbe posits that this idea might be manifested in the spiritual acquisitions made possible during these days. While Yom Kippur can sometimes foster certain feelings of rebellion, the tremendous outpouring of Hashem's love experienced on Purim negates any feelings of hesitation.
The essence of Purim is the heart. Love is the focal point of all the mitzvos of the day: Love of Hashem (Megillah), love of fellow Jews (mishloach manos, matanos l'evyonim) and even love of oneself (seudas Purim). On Purim our hearts are opened wide and it would be a shame if all we fill it with is candies and lightheadedness. It's a once a year opportunity to get "drunk" on love of Hashem and feel a true connection to every person in the Jewish Nation!