My goal with joining Facebook group is pretty much the same reason why I started teaching on Skillshare - to build my audience. I have followers on social media and other platforms but still very few "fans" who look forward to buying my next work - whether it's a book, video or other media.
I do have a few regular students / coaching clients who study a range of things related to self-improvement, creativity, marketing, and so on. But I want to grow beyond this to help more people. As Zig Ziglar would say, you can have anything you want if you just help enough people get what they want.