It does make me very curious now. They do make a living, so they must be influencing somebody.

That's not actually a necessary conclusion. It means someone(s) THINKS that influencers are positively impacting sales or whatever, but advertising roi is difficult to actually calculate.

Some influencers ask you to use codes that will associate your purchase with them, so there's there. Plus, I get the sense that at least some of them don't get paid unless people make a purchase with their code, so, pretty low level investment for a company.