Tesla was already built before he arrived? You don't know what you're talking about.
Tesla, the car, was not, but we are clearly talking about companies, not cars.
Is it that you are unaware of the difference between companies and cars?
How big do you think it was exactly when he joined? And at what level of product maturity?
1%. It is at 2% now. Which isn't a knock on what Tesla is doing today, but to tell how it pales in comparison to what the company will be doing 1,000 years from now. We are still in very early days.
If that is how you want to measure it, Tesla hasn't been built yet. It is still under construction. No matter how you slice it, it is impossible for Musk to have built Tesla.