A new festival bursts forth from the darkness
Chiddush heard from Moshe-Mordechai van Zuiden: Why did the date of the decree to destroy the Jewish people fall on 13th Adar? Because that's the day furthest away from Pesach. The next day, 14th Adar, we already begin to plan towards the next Pesach as it says in the Shulchan Aruch, 30 days before the festival we begin to plan.
This tremendous idea got me thinking. From the very darkest place, where the light of redemption was the dimmest, a brand new festival broke through, an entire marvelous new festival of redemption (with yet more eating, of course!). From within the darkness the most amazing things are born.
Such born things may differ from their source in unexpected ways. The Purim energy is not by any means identical to the Pesach energy. The latter seems clean, clear and straight, while the former seems dark, concealed, twisting and turning. I would go so far as to suggest that this world is divided into Purim people and Pesach people. (I know which one I am... which one are you?)
In any event it's good we have both. So thank you Haman - couldn't have done it without you.