DaveMage
Slumbering in Tsar
However, I am sure that one of the reasons it was designed in the manner they did, was to specifically target a younger crowd...as has already been discussed and argued ad nauseum. The fact that a significant group of long term gamers prefer the system is less about a purposeful marketing focus as it's simply about the fact that they like D&D, in any iteration.
I think that another of the reasons it was so different from prior editions is to assure the OGL was not used by some 3rd party to create a clone of the game.
(As Ryan Dancey once indicated - paraphrasing - that in order for D&D to ever be closed again it would have to be radically different from D&D as we'd known it. Voila - 4E!)