If the good Doc wishes to make widely known the reasons for his departure, he could have done so very easily.
That he has not may mean he wishes to keep it relatively quiet, or that as expected he remains the consummate professional, and probably both.
It is good he has a loyal following, with plenty of appointments to justify his being taken on at V&P, and as far as I'm concerned he is a bloody good Doc along with being a top guy.
For those that feel the urge to find out, why not just ask him. I suspect the reason is a lot simpler than the conspiracy theorists are conjuring up.