How was the creation of the Constitution represented as a great vision for the nation's future on the part of the men who created it?
The way that this question is worded implies that you are supposed to be discussing how the creation of the Constitution is represented in a particular book or article or other document. Without knowing what work you are supposed to be discussing, we can only talk about this in generalities.
In general, the creation of the Constitution is depicted as a “great vision” by the fact that textbooks and popular culture tend to say that it was the work of geniuses. We talk about the “Founding Fathers” and we argue that they were so well-read and such great political thinkers that they were able to create a Constitution that would still be effective over 200 years after it was written, in a country that would have been all but unimaginable to them. We are generally told that the Framers (we capitalize their “name” to show how great they were) were men who borrowed from intellectual theories like those of Locke and Montesquieu. We contrast them and what we see as their selfless intellectualism with our narrow-minded politicians today who are simply trying to get reelected. In these ways, we portray them as in some ways superhuman. We portray them as geniuses who had an amazing vision for how our country should be governed.