http://revach.net/article.php?id=3508

Section: Moadim   Category: Megilas Esther
Haman Is The Architect Of His Humiliating Downfall
With regard to Haman's downfall the U'Masok HaOr brings from HaChaim V'Hashalom that there are two ways Hashem saves Klal Yisroel from our enemies.  One way is like Hashem did in Mitzrayim.  Hashem pulls out all the stops to demolish our persecutors.  Ten brutal nature altering Makos one after the other in vicious succession.  Similarly by Sancherev whose massive army laid siege on the hopeless Yerushalayim and was poised to strike a fatal blow, Hashem miraculously wiped them all out during the night.  This show of force, while devastating, is not embarrassing.  In both these cases the victim has been bested by forces far more powerful than they are expected to handle.

Another way that Hashem pays back our enemy and provides a salvation is by sending our oppressor into the trap he has laid for us.  This is totally humiliating as the cunning calculation and great pride that went into preparing our downfall not only did not provide the desire result but our enemy now finds himself lying in the very grave he prepared so meticulously for us.  This was the downfall of Haman.  The very same tree that he so proudly prepared was the tree he himself hung from.  This was the theme all along even before Haman's final death.  He schemed to wear the King's clothing and ride his horse by himself, yet he was the one pulling along his arch enemy in disgrace.

This theme repeats itself throughout the megila as a careful look will show Haman's hand in other events, and they all came back to haunt him.  The path Haman paved to the top was simply a path he was preparing for his way back down, far down.