"The Lord said, 'Behold, they are one people, and they all have the same language. and this is what they began to do, and now nothing which they purpose to do will be impossible for them. come, let Us go down and there confuse their language, so that they will not understand one another's speech.'" (NASB)
So let me get this straight... Civilization is clicking along, everyone's cooperating, people are speaking the same language, building great monuments and temples, and along comes God. He whammies them, and strikes a dissonant chord in the harmony they had created.
Why would he do that?