From where do we learn we need a theme on Purim? From Haman, who asked for three things (crown, robe, horse) to create a theme of malchus. This also indicates that, like the dinim of chazakah, it requires 3 items for a theme. The problem is, Achashveirosh only gave him 2 items. Does that mean achashveirosh didn’t require a theme?
It could be that Achashveirosh felt that to go without a theme is pikuach nefesh, and by pikuach nefesh 2 is a chazakah…