If we look at how the new generation of social platforms are built - in China - then creating the user base is not so hard anymore. Tencent and Bytedance are paying Influencers to use their platform and create content there. Once the user base is built up that way, you introduce advertising.
I'm currently working at a company with no upper management, and peer reviews. It's not by design, but I suppose it's "flat" because of this - upper management have left or quit, or they haven't been able to find them. Lots of infighting.