Outside companies almost never get the same benefits as local ones, that's true even outside of china. Another thing is that china has national interests in chinese carmakers.

So long as they keep the Chinese government happy. That's a big lever China has on Musk.

Tesla needs to make a certain substantial profit margin, same problem as Apple's car project. BYD will sell at a loss for years to monopolize like Amazon/Walmart etc.

BYD has a level of vertical integration far beyond anyone else in the industry.

Chinese companies aren't buying detestable social media platforms and speedrunning them into the ground.