Why does Tesla open patents?

On the surface, it is to serve the public and use their own patents for free. The real purpose is to give him a free publicity report for the global media. In fact, all patents issued by Tesla are patents whose protection period is about to expire. In fact, Tesla still has many new patents pending. These patents are not authorized, so they will not be released, and of course they will not endanger their own interests. They will not only get a good reputation, but also let the global media promote them for him. Everyone knows the trick.