If it is true that Achashverosh had his wife killed for refusing to display herself in the nude at his party, Achashverosh must have regretted such an extreme punishment for so minor an offense. Considering H-Shem’s consistent use of “mida kineged mida” (“measure for measure”), Achashverosh realized that Vashti’s misuse of Jewish servant girls on Shabbos precipitated in her punishment being dealt on Shabbos.
The Talmud (Megillah 12a) tells us that she caused her Jewish maids to go around unclothed.
The Maharil Diskin asks why this has to be noted. Was it not bad enough that our sisters were forced to desecrate the Sabbath? Did their forced immodesty truly add to Vashti’s evil? He answers that Vashti’s participation in this was especially worthy of punishment because one can reason that poor servants surrounded by expensive goods may attempt to steal what their eyes see. One might think that nudity might thus be a legitimate way to curb theft, leaving potential thieves with less opportunity to hide their loot. (It has been reported that current manufacturers of illegal drugs use this very method with their employees.) However, it was especially evil of Vashti to force the Jewish girls to go unclothed on Shabbos because they would not have stolen, anyway, seeing as theft, coupled with the fact that carrying an object from one domain to another is forbidden on Shabbos (Mishnah, Shabbos 1:1), would have definitely prevented the girls from stealing.
Likkutei Anshei Sheim point out that the 180 day feast was held in the beginning of Vashti’s third year of being queen. This means that she had two full years (354 days twice) and the 180 days (354×2+180=888 days), which divided by seven, come out to be 127 Shabbosos (888/7 = 126.857143)1. For causing Jewesses to desecrate 127 Sabbaths, Vashti lost the reign over 127 states.
Tangentially, the Chasam Sofer adds that Vashti’s Sabbath desecration was part of the reason for the mystical custom (see Zohar on Bireishis 17b, Shulchan Aruch Orach Chaim 297:4, Mishnah Berurah ibid., sub-paragraph 8) to use myrtle leaves for the spices in the Havdalah service after Shabbos. Since “Hadassah” (Myrtle) was one of Esther’s names, her defeating Vashti’s influence was alluded to in the verses in Yeshaya that we read on fast days (55:13, 56:4), in which the myrtle succeeds “from under [or, instead of] the thorn-bush,” (see 2:4 and 2:17 below for similar verbiage) the thorn-bush being the prickly Vashti, who caused Jewish girls to sin on Shabbos.
1Mathematically, one can round up to 127, or perhaps we can consider the last seven days as an additional week. Perhaps Vashti’s not surviving the whole day would account for the fraction missing from the whole number.