Did Charlie Gibson really "retire" or did ABC ask for a divorce?

I am just wondering about this Charlie Gibson/Diane Sawyer thingy over at ABC. I mean, these networks like to force people into retirement (Star Jones on the View comes to mind), but in fact, they are firing the individual and making the individual say they are “retiring” or “seeking other possibilities.”
It is curious that Diane Sawyer is being tapped to replace Charlie. It almost seems like infidelity to me. And really, is this a true, bonafide retirement? Or did ABC not only ask Gibson for a divorce, but they commandeered him into checking out of the marriage, gangster style?
Something’s slightly fishy about this whole brouhaha….maybe Charlie was too high maintenance?