R. Hutner explicates the well-known relationship of hishtadlut vs bitachon - personal effort vs trust/faith in God to provide. He finds a mirror to this duality in the relationship of Purim to the rest of the year, through the lens of the mitzvah of erasing Amalek.
An exploration of Pachad Yitzchak: Purim 34. A comparison between Purim and Pesach, focused on Purim's unique relationship to the theology of a "hidden" God.