I suspect that at that level, everyone knows where every one else's bodies are buried. So unless you are prepared to deliver a knockout punch, its probably best to be polite.
It is a simple back scratching technique used by all administrations. Clinton did not probe Bush #1 and left it alone. Bush # 2 will not start picking at the Clinton goons. The pairing of Bush #1 and Clinton is creepy. I agree with Peggy Noonan. Berger is ready to serve again. He will be on tap to work with the next Democrat administration. He is a true soldier for the left.
I think that the President knows that he did it after being asked by someone else - whether it was for loyalty or because someone had something hanging over his head. Maybe he was boxed into a corner and the WH knows what really happened. It is still wrong of course, but I don't think we know the whole story either.