Do you have data for this?

Tesla had, essentially zero growth in the US in 2019, which is where it sells half of its cars. There are many companies that had higher growth than that, including Volvo, which grew 10% in the US. LandRover sold 125k units in the US in 2019, which is far more than the Model S + X (its competitors).

So, I'm not sure where you get the idea that everyone else is shrinking while Tesla is growing. Some companies might be, but some are growing faster than Tesla. These are not mysteries; there is data out there.