This is such a crazy way of thinking about Elon. What would this gain him exactly? Attention doesn't make money, attention doesn't help growth. And doing that now because attention would go away in a couple years makes zero sense.
Musk literally always does the same thing, he comes out, talks about a bunch of things he wants to do and then goes and does them as well as he can. He has done that for 20 years and yet still people come out with the 'Elon is doing 4D mega brain level marketing' every single time. Even when he is wrong he goes out and does it anyway until he is forced to correct course.
Elon in fact does believe that by 2030 he will sell 20 million cars, and he most certainty is not content with being a 'smaller minority part of the industry'. Did he stop when he managed to get Falcon 1 to orbit and make a nice buissness out of that? No, he went on to the next bigger thing. The same thing for the Falcon 9 transition to Starship.
What makes much more sense is that they wanted to show of the level of technology they have an recruit more people to this effort. They also want to light a fire under the competition ass and show the people how the ICE age is ending. Literally the exact same thing they did with the Gigafactory in Nevada, when people said 'oh he wants to create the biggest battery factory in the world, that is pure hype and marketing' and now they have the biggest battery factory in the world.