You are right. Being a Facebook influencer is not only about having followers but also about sharing good, positive stuff that people can enjoy, administer in their lives, or share to help others.I have looked into being a Facebook Influencer but it's not something I have gone ahead and attempted to do.
From what I understand, it's not just about having many followers but also the content you share and how many people enjoy your content and find your content to be helpful.
They generate a lot of revenue though. Being a Facebook influencer is like a film celebrity in real world. It's money everywhere.
It is easier once you establish your profile or page. People will approach you with offers most of the time. There is almost no need to go begging for paid posts unless you are ambitious.