Mordecai establishes Purim as durable memory

Mordecai writes a yearly memory of reversal, not a revenge charter

And Mordecai wrote these things, and sent letters unto all the Jews that were in all the provinces of the king Ahasuerus, both nigh and far, to stablish this among them, that they should keep the fourteenth day of the month Adar, and the fifteenth day of the same, yearly, as the days wherein the Jews rested from their enemies, and the month which was turned unto them from sorrow to joy, and from mourning into a good day: that they should make them days of feasting and joy, and of sending portions one to another, and gifts to the poor.

The lot that scheduled death becomes the name Purim

And the Jews undertook to do as they had begun, and as Mordecai had written unto them; because Haman the son of Hammedatha, the Agagite, the enemy of all the Jews, had devised against the Jews to destroy them, and had cast Pur, that is, the lot, to consume them, and to destroy them; but when Esther came before the king, he commanded by letters that his wicked device, which he devised against the Jews, should return upon his own head, and that he and his sons should be hanged on the gallows. Wherefore they called these days Purim after the name of Pur.

Therefore for all the words of this letter, and of that which they had seen concerning this matter, and which had come unto them, the Jews ordained, and took upon them, and upon their seed, and upon all such as joined themselves unto them, so as it should not fail, that they would keep these two days according to their writing, and according to their appointed time every year; and that these days should be remembered and kept throughout every generation, every family, every province, and every city; and that these days of Purim should not fail from among the Jews, nor the memorial of them perish from their seed.

Purim is durable Jewish memory: rest, food, mutual portions, gifts to the poor, and a story of a lot turned. It is not inherited revenge, not a yearly license to harm, and not a code that maps Haman onto modern Persians, Iranians, or any other people. God is still not named in the founding letter.