Since Pharaoh denied Hashem’s existence by saying “Who is Hashem ... I do not know Him,” a major purpose of the Ten Plagues was to show the world that that there is only one G-d, Who is the Master over all the world’s creations. The question is, why was it necessary to afflict the Egyptians for months with ten individual plagues? Wouldn’t it have sufficed to smite them with one “MegaMaka” - one huge plague that would encompass all the afflictions together, to demonstrate Hashem’s mastery over nature and force the Egyptians to free the Jewish slaves? Similar to the U.S. dropping atom bombs over Japan, which brought an immediate end to the second world war!

     R’ Chanoch Ehrentrau zt"l (Kometz Hamincha) answers that proving and convincing the world - and Pharaoh - of Hashem’s mastery over nature was a gradual process and could not be accomplished by one “mega-maka.” Why? Because just as people get inspired quickly, they can just as quickly lose that inspiration. Constancy and repetition is necessary to retain any impact one wishes to remain part of him. Consequently, even though one huge plague might have succeeded in convincing Pharaoh to release the Jewish nation from Egypt, nevertheless, the recognition of Hashem’s mastery over the world would have only been short-lived.

     Likewise, there is no doubt that Bnei Yisroel believed in Hashem, as is evident from their constant tefillos begging Him to redeem them. And yet, this knowledge was based on a legacy they received from the Avos. However, before redeeming His people and giving them the Torah on Har Sinai, Hashem wanted us to also have a sensory perception of this concept so that it would make a lifelong impression on His people. "אינו דומה שמיעה לראיה" - “Hearing is not the same as seeing.” Thus, during the ten makos, Hashem changed the laws of nature to prove to them beyond any shadow of a doubt that He is the sovereign power over the world.