On the one hand, Purim, that commemorates a narrow escape of Persian Jews from the death sentence 2,500 years ago, fits perfectly into the regular scheme of a Jewish holiday: 'They tried to kill us, we survived, let's eat.'
On the other hand, there is some sharp contrast between Purim and other Jewish holidays, like Pessach or Chanukkah. The latter are about Jews escaping death, too, but there were miracles happening there: The division of the Red Sea, or the light of the Menorah that lasted eight days instead of one.
In the story of Purim we do not see God acting (he is not mentioned once in the whole Book of Esther that is read on Purim). The events that led to the lifesaving victory of the Jews seem perfectly natural. Esther's uncle Mordechai just happens to be in the right place to learn about the plot of Haman, the king's minister, to kill all the Jews, by persuading the king that they are dangerous for the state (typical anti-Semitic argument!); Haman just happens to erect the gallows on which he was eventually hanged…