it comes from a marketing term. influencer used to be someone you find in schools or work places; popular people that matter because they are fashionable, experts in something, or have a lot of value in their community/area of expertise.
for example, MJ was an influencer because of the insane skills as a player. Same with the kid at school who always, somehow had the newest sneakers before they were in stores.
companies would try to find them and bring them in for focus groups and/or provide them with prototypes or first editions to test the market.
influencers now are just people with a lot of followers. the more eyeballs people have on you, regardless of your actual skills or opinion, the better.
Charleston White has no actual skills or expertise and is an influencer. Same with Adin Ross and Sneako. They are just shock jocks with a lot of eyeballs. No different from Howard Stern