It’s all opinions. IMHO something is rotten at Apple. Often is. Take a look at their macOS releases and their stability. I could be wrong. I’ve been wrong many times before. I hope I am wrong and that this was a good move for them.
To be fair, they are maneuvering an unprecedented transition, during a global pandemic. Also the chip team and OS/software team are not the same thing. That being said, we simply have no idea why this man left or what his impact will be. We do know that there are several key players still at apple, like Srouji, who didn’t leave Apple even after he was offered the CEO position of Intel, and Sri who is a key player in all Apple silicon, among many others.
These articles saying this one dude is responsible for the apple silicon transition are exaggerated and dramatic. In reality no one person is responsible for this, and Apple has many engineers on their team who are all extremely smart and talented.