If it were that simple to sway markets through marketing, we would see Pepsi/Coca-Cola or McDonalds/BurgerKing swing like crazy all the time from "one well-placed ad campaign" to the next. We do not.

Thanks to well-placed ad campaigns, people have a very good idea what Pepsi, Coca-Cola, McDonald's and Burger King are. They also know what Siri is. And it would be similarly easy to establish Gemini as a household name.