Yes MySpace was created by marketing people, but that's the reason for both its initial rise and ultimate stagnation. Marketing people think "features" is the name of the game. Zuckerberg, like a good nerd, had the understanding that "platform" is really the name of the game.

Plus Zuckerberg's massive anti-privacy bias caused him to push the product in the right (superior product/market fit) direction in the face of significant user complaints (i.e. beacon).

And the speed at which facebook has been able to re-invent itself multiple times (e.g. platformization and twitterization) has been very impressive.