Here the Lord points out under what kind of impression mankind would be they were able to finish building the tower. They will start assuming that they can do anything. Then their delusion that they can acquire divine power will only be strengthened, which means that mankind will go from bad to worse.
It is necessary for man that the Lord God makes him understand that he is not his equal. Nor could he ever be. And for this reason the Triune God decides to intervene at this juncture.
6 And the LORD said, “Behold, they are one people, and they have all one language, and this is only the beginning of what they will do. And nothing that they propose to do will now be impossible for them.