R’ Dovid Feinstein writes that the expressions are written in a different order than the previous verse (Esther 9:18) because the original celebration was spontaneous, and not following any specific rules. Mordechai would later (Esther 9:21) establish Purim for future generations with changes.
Yosef Lekach notes that everything mentioned in the verse needs to be artificially “made.” In that first year, happiness was a natural, organic reaction. In the future, it would have to be manufactured artificially.
Malbim writes that the Jews did not feel the need to celebrate the first year because they didn’t know the decree and thought that their victory was due to the king’s decree.
R’ Yehonason Eibshutz and the Chasam Sofer note that in the first year, the Jews accepted Purim as a Yom Tov, so Mordechai expected them to feed the poor.
After all, the Rambam (Mishneh Torah, Hilchos Yom Tov 6:17) writes that people have the responsibility of feeding the poor on a Yom Tov. Later, when the people would not see Purim as a Yom Tov, the order was switched around in order for the people to still feel responsible for feeding the poor.
Rav Gallico stresses that the verse mentions the Yehudim celebrating to point out that they did so despite their necessary exhaustion.
With the Jews in Shushan still struggling, the Ginzei HaMelech notes, the Jews’ celebration of persumei nisa (“publicizing the miracle”) and feasting was intended to inspire the remaining Jewish warriors.
In his introduction to Yosef Lekach, Rav Eliezer Ashkenazi notes that a significant difference between Chanukah and Purim is that one is not required to celebrate Chanukah with a feast, per se. Since there were Jews still perishing in battle on Chanukah, we cannot institute a national feast. On Purim, however, the celebration requires both feasting and joy because not one single Jew died.
According to the Ben Ish Chai, we need both actions to celebrate both the spiritual renewal, and the physical safety.
The Sfas Emes emphasizes this by noting that, grammatically, the verse uses the word v’aso (“and he made”), implying that H-Shem made this into a day of joy and celebration.
R’ Yitzchak Hutner notes that any holiday from the Written Torah requires a degree of joy, as the Rambam (Mishneh Torah, Hilchos Yom Tov 6:18) makes clear. The holidays from the Oral Torah require drinking. Since this holiday contains aspects of both the Written and Oral Torahs, Purim requires both joy and feasting.