Social media as a cultural phenomenon is downstream from the technology that enables it.

From first principles it makes sense that culture is downstream from technology. Inventing tech is uncovering the mysteries of the Universe, and as they get uncovered by bright individuals, the masses adopt the things they enable. You couldn't have had social media in the Middle Ages, even if people had wanted them (which they didn't, we needed intermediate technologies like the printing press, electricity, radio communication, computers, the internet and smartphones for that desire to even emerge).