If Coca Cola stopped advertising for a year, their sales would surely start trending down.
The mechanism of how advertising works seems to be not that. I think repeatedly brand exposure does something to the brain and decision making that we don’t fully understand.
Exposure breeds familiarity, which breeds desire, I think.
Even if all you hear is an occasional ad about the company, you might get curious and research them yourself.
I'm sure it's almost completely subconscious.