Here is my thoughts. McVay is the type of guy who is incapable of believing that he is at fault. No blame there. To be great in combat that is an absolutely necessary trait to have. With that in mind:
He believes that Goff is the reason for failure. This has become more and more evident as weeks go on. McVay has been more inclined to completely blame others in the media.
Goff is a nice guy. Not hot headed. Loves everyone and liked by everyone. Laid back. The polar opposite McVay. In fact, these types of personalities are completely incompatible.
This has boiled to a head recently. McVay has been waaaay too loud. He showed his cards. Goff comes in and wins the game in the first game. Goff plays good in the last game...but McVay doesn't.
Remember that McVsy does not believe that he is EVER wrong. He is frustrated and is doubling down. Most coaches would be quiet but McVay fuels it.
I'm a McVay guy but he HAS to see that he is not what he believes he is. His schemes are not impervious to failure. He has been figured out. He had his chance with all of the right personell but HE got outcoached in the super bowl. He struggles with in game adjustments but he refused to accept that so it HAS to be others.
Here are some more thoughts on McVay. The dude seems pretty miserable to be around. He wants his players, his coaches, his way. His coaches leave him and they prove that they are better than him. He doesn't like that.
I don't know if Goff is the guy or not but I do know that McVay needs to grow up a bit and stop being so emotional. There has been a lot of turnover in a short time. At some point you have to wonder if it's not EVERYONE else.