(Courtesy: Revach L'Neshama)
The gemara (Sanhedrin 21b) says that originally the Torah was written in Ksav Ivri and only later in the time of Ezra HaSofer was the Torah given in Ksav Ashuris (our Ksav today). What is the significance of this change and why did it happen in the time of Ezra?
Rav Levi Yitzchok of Berdichev in Kedushas Levi says that the prelude to Ezra and the building of the second Bais HaMikdash was the Nes of Purim. Krias Megilas Esther was accepted by all of Klal Yisroel two years after the Nes, and in the next year the Bais HaMikdash was built. The reason for this, explains the Berdichever, is as follows.
The gemara says that after the Nes of Purim Bnei Yisroel accepted the Torah in a way that they hadn't accepted it at Har Sinai. At Har Sinai they recognized the power of Hashem to override Teva and do with it as He pleases breaking every and any rule. They did not recognize however Hashem also has the ability to work within Teva. Only after seeing Hashem manipulate politics and clearly orchestrating a series of happenstances in favor of Bnei Yisroel during the dark times of Haman, did they finally understand that all of what happens and all that we see, is not merely natural world order but rather Hashem's will and choreography, albeit in a hidden manner.
The Seforim say that Hashem created the world with the 22 letters of the Aleph Bais. This might seem beyond our comprehension initially, however we must understand that the Aleph Bais are not shapes but rather different manifestations of the power of Hashem. In Shamayim there are no shapes for the letters as no shape can hold the unlimited power of each letter. The shapes of the letters of Ksav Ashuris are depictions of these powers as they appear in this world of natural limitation.
After Purim with the acknowledgement of Hashem's power within every mundane substance and event, we were zocheh to receive the Aleph Bais, itself a worldly exterior to infinite power. The concept of the materialization of Hashem's presence in the world paved the way to the materialization of power of Hashem within the Aleph Bais.