If the fact that a soda company can suborn an ancient figure like Saint Nick so completely that no one remembers it happened doesn't drive the point home then consider this: Diamond engagement rings are a deliberately ad-created "tradition".
https://www.theatlantic.com/international/archive/2015/02/ho...
I'm just supporting what the other poster said about advertising not always having the intended effect.
There are some brands I actively avoid simply because I didn't like their advertisements, or how often they advertise and others where no amount of advertising will convince me to use their product (like Coke for example, because I think it tastes vile and I know it's basically just unhealthy sugar water).
And I agree with you about advertising and unintended effects. To me modern life seems more and more like a giant open-ended experiment, one with no control group...
And that version of Santa Claus was still based on fictional folk characters from history.