Reasonable people can disagree with this thesis.

What is the counter argument?

I'm not arguing it one way or the other, but the obvious counter is "Tesla's success was orthogonal to, or in spite of, Musk."

You'd have to provide some pretty compelling reasoning to support that Tesla is successful in spite of Musk; i.e. that without him, its market cap today would be higher than 780 billion dollars.

Even discounting all other data, Tesla avoided bankruptcy in 2008 only because Musk tricked a key investor into believing that he could personally finance their investment round if the other investors didn't sign.

You'd have a hard time tracking down a single eligible CEO who could play that role in 2008, let alone get them in a position to actually be with Tesla at the time. And this is only a single example of a pivotal moment during Tesla's history that hinges on Musk.

Without Musk then, no Tesla today.