I think you're confusing authenticity with DGAF, because they both look like the opposite of insecurity.

Trump and Hilton play a DGAF role on TV, but the very fact that they're putting in the effort means that it isn't authentically them. If they really didn't care, we wouldn't know their names, because being wealthy doesn't automatically make you a celebrity. Consider Michael Bloomberg, who briefly flirted with a presidential run, but then discovered that coming from legit middle class roots and achieving orders of magnitude more wealth than Donald Trump meant very little next to the decades of work Trump had put in to build his celebrity status.

As celebrities, they have embraced caring about what people as their job, and for them, part of that job is playing out the ordinary person's fantasy of not having to care what people think -- a role that is only authentically them in the sense that they learned it authentically as spoiled rich children.

A lot of people experience anxiety in their everyday lives over how other people will perceive them. "Did I do a good enough job? What are people saying about me? What do people actually think about me?" When Trump and Hilton ostentatiously act out being able to be dumb and inept and still being treated like they're amazing, it's the perfect inverse of what causes ordinary people anxiety, which makes it a perfect fantasy.