Being an influencer is the new big thin to get rich in this era. It is not about being a celebrity, but to be someone who can influence the people that looks up to you. Your fan base is your network, they are the people who can sell your business to everyone without you breaking the bank for Ads. Like the example you gave, Kim Kardashian is a highly endowed figure to women, most young females want to be just like her, most men simp on her too, while other genuinely like her personality. So yeah, she will definitely sell out on her first day.
These days, being an influencer is like having your own media channel and community, all in one. It is less about old-school "celebrity" status and more about actually moving people with your voice or your story, no matter what you are selling. Your network is your true marketing team, and half the time, you do not even need to pay them. They share and hype what you do because they feel connected. Kim K "brand" is a mix of her story, her confidence, the image she projects, and yeah, even the controversy. Some people want to be her, some want to be with her, but the effect is the same: whatever she puts out, it gets attention and usually sells out
There is a thin difference between the way influencers and celebrities relates with their followers. Influencers creates a personal connection with tier followers, it becomes as if they are in the same scenario or situation as them. So people with similar interest know ow they feel. But for the celebrities, they barely communicate with their followers, very rare you see them make comments too. They are more focused on maintaining their high profile reputation secured. In the end, influencers build more trust than celebrities'.