The assumption that the "best professors" must lead to the best learning outcomes didn't start with MOOCs. It's a reply of patterns that we see time and time again in technology and learning.
It was my provost Carol Matteson at Rowan University in Glassboro NJ in the mid-1990's who first started my awareness of the profound impact technology would make on the higher education process. It was at that time I first heard the now-tired phrase: "We need to move instructors from being 'The Sage on the Stage' to 'The Guide on the Side'". In other words, the massive availability of content, and the affordances of technology enable us to best assist our students as a kind of coach and mentor, rather than a priestly authority figure speaking from an elevated lectern. I have found this idea to be a major inspiration on how I think about educational transformation.
But despite the "guide on the side" rhetoric, the thrust of educational technology has often focused on building a bigger and better stage. The movement to create "smart classrooms" was mostly about giving the instructor bigger and better tools to lecture - projectors, screens, document cameras, a computer (possibly the only one allowed to on in class), even microphones and speakers, all designed to enable a multimedia performance. Yes, there have been some innovations that directly touch the student, but even there they tend to have an asymmetric effect that reinforces the special role of the instructor, rather than putting the student at the center- clickers* come to mind.
Now MOOCs have recapitulated this same tendency - rather than challenging the notion that, in a connected world, knowledge does not lie only with a special class of priestly individuals, most (but not all!) MOOCs seem to be built around a model that emphasizes the brilliant and noble professor, up on the (digital) lectern above us, enlightening the world. Of course, the phenomenon of the TED conference and videos has proven that we hunger for good (and entertaining) explanations of the world. But the deepest learning takes place when the learner becomes the agent of his or her own learning. The "sage on the stage" pushes us in the opposite direction towards the passive acceptance of expert knowledge and opinion. Just open your brain and let the learning pour in.