I think people find their own level. You only have so many hours in the day to be aware of the world around you, and some people choose to click on the DM sidebar and read about sideboobs and Kardashians, some people read about climate change and the migrant crisis, and some lucky souls read both (!).
The Kardashian/Cheryl F-V et al brands are intentionally directed and marketed at their respective audiences as part of a wider marketing campaign. The livelihoods of several members of the Kardashian family depend on those clicks and shares - the minute they stop being "relevant" to their audiences, their revenues will drop off sharply. So with that being the case, I don't really mind their prevalence - they're making a living. It's not like people accidentally know what Kylie's new puppy (bunny? I can't remember) is called (Bruce, if you're interested) - her well paid PR team strategised the Instagram post, just as Kanye West strategises the way he speaks (his mother was a high ranking academic before she quit to manage his career - he's about as "street" as Nigella Lawson), and timed it, pushed it out to the press, and that in turn feeds in to the Ferrari her boyfriend bought her for her birthday - Ferrari gets press, we know who Tyga is (some of us, anyway) and it reopens the (already rapidly dwindling) conversation about Caitlyn Jenner's gender.
It's all meticulously planned out (although Kanye kind of does his own thing a bit) and finely targeted towards the "right" people to buy into (and quite literally - to buy the products expensively name-checked in Kylie Jenner's Instagram, to buy Ri-Ri perfume etc. etc.) and I don't think you can blame people for following brands like that - I'm wearing Jack Wills jeans because I bought into their branding. It's a thing we do.
India Knight said something about television a few months ago - she was cross with people being snooty about it and said that it is still a part of our culture, even if you think you are "better" than it. The Kardashians and everything they imply are a part of the tapestry of Western culture right now, whether we like it or not, and not to know anything about it is not something to be smug about.
TL;DR: Some people like the Kardashians, and that's okay.