As drips and drabs come out, it continues the same theme: Mcvay lost trust in Goff as a guy who could get it done.
Snead has always said the goal is not winning the West, it's winning Superbowls. And I imagine McVay feels the same or they wouldn't have hired him.

They thought they had the QB in Goff that could lead them there, in the way McVay wants of his QB. He didn't..... seemingly couldn't.... do it.

And it doesn't take a sports analyst to see what was happening. Indeed, we all saw Goff making head scratching throws. Missing wide open Receivers. Seemingly having no pocket presence or a clock in his head that said to get rid of the ball.

I won't pretend to know why all this happened..... but it did and it was obvious.

McVay didn't want to keep tutoring Goff, he wanted Goff to become the Master.
I can only think that he thinks Stafford already is the Master and now it's a matter of turning the reins over to him.