This is a bizarre example, sort of like using Bill Gates to show why nobody needs to work for a living. It ignores the extreme inequality of fame.
Tesla doesn’t need advertising because they get huge amounts of free publicity already, partly due to having interesting, newsworthy products, partly due to having a compelling story, and partly due to publicity stunts.
However, this free publicity is mostly unavailable for products that are merely useful without being newsworthy. There are millions of products like this. An exciting product might not need advertising but exciting isn’t the same as useful.
So It seems like the confidence to advertise a boring product might be a signal of sorts? However, given that many people in business are often unreasonably optimistic, it doesn’t seem like a particularly strong one. Faking confidence happens quite a lot.
What’s an example of a misconception someone might have due to having a mistaken understanding of causality, as you describe here?