As in many aspects of Jewish life, myths abound concerning the Purim story. One of those myths portray Achashverosh as a harmless, bumbling old fool, pulled to and fro by his wives and advisors. Yet Gemara Megila makes it abundantly clear that Achashverosh hated the Jews no less - perhaps even more! - than did Haman, and yearned for their destruction. As proof of this, they point out that when Haman offered 10,000 talents of silver to the king so he would approve Haman's plan to wipe us out, Achashverosh refused the gift! ("The silver is given to you," said Achashverosh to Haman, 3:11). And yet the Megila opens with an elaborate, orgiastic 6-month revelry (which makes Mardi Gras and Carnivale pale in comparison!) to which the Jews are cordially invited & even served Glatt kosher food! (see 1:8 - "The king commanded his officers to fulfill every man's pleasure").
At this same meal, the Jews watch aghast as Achashverosh appears dressed in the clothes of the Kohen Gadol, and then brings out the holy vessels of the Bet HaMikdash from which to drink and eat.
What is going on here? What message is Achashverosh trying to convey, by both inviting the Jews to his banquet and then doing some-thing that shocks them to the very core? And what happens to make both Achashverosh and Haman decide to solve their "Jewish question" once and for all? The answer to these questions go the essence of what Megilat Esther is REALLY about.
Like many rulers in history, Achashverosh is willing to tolerate the Jews, to welcome them even, because he knows how "clever" Jews are, how good they are for business, what excellent advisors they make. Mordechai joins the ranks of Joseph, Abravanel, Daniel, et al, as expert counsel to the royal court. Achashverosh is even willing to accommodate the special needs of the Jews, their meals and minhagim, because that represents no threat to him. But one thing he cannot abide: He cannot permit us to fulfill our ultimate destiny of living in our own land, under our own rule, with our own Bet HaMikdash. By wearing the garments of the Kohen Gadol he sends the message: "You Jews can practice your faith here as a minority, but you are NOT going back to Jerusalem, you will NOT rebuild your Bet HaMikdash and re-establish the Avoda; you are confined to the Diaspora." He will tell Esther more than once, "Up to the half of the kingdom, and it shall be granted to you." What is the half he will NOT grant? The restoration of Jewish sovereignty - that alone is not up for discussion.
What changes his disposition and turns him into a partner to genocide? Mordechai! For Mordechai is a proud, uncompromisingly courageous Jew, a member of the Sanhedrin that is a major component of our national identity, a potent symbol of our nationhood and spiritual supremacy. When Achashverosh is confronted by Mordechai - who will have none of the "Diaspora mentality" practiced by his co-religionists - he accedes to the urgings of Haman and seals the edict of our destruction.
But Hashem hears our cry and sees our Fast; He answers our prayers and reverses Achashverosh's mindset. Haman is executed & Achashverosh becomes the very instrument for the Bet HaMikdash to be rebuilt, through his and Esther's son Darius II, who renews the decree of Cyrus to allow the Temple to be restored. This is the crucial post-script which permits us to celebrate Purim at all, for while only events which occur in Israel can become national celebrations, Purim is accepted because it's ultimate purpose is the restoration of the Temple.
The message of all this is obvious: We may enjoy periods of prosperity and popularity in the Diaspora; we may get oodles of kosher noodles and the accoutrements of Yiddishkeit in countries around the globe. But the focal point of Jewish life must be to re-establish ourselves in our own Land, operating under our own rule, fulfilling the Torah to its fullest. When that becomes our collective mandate and our mission, we have a fighting chance to restore the Sanhedrin, bring Moshiach, and usher in the Geula.
Anything else is just a mask.