How do you find a good space to bet into for a new Social Media platform?
Expressing one's identity has always been an essential part of the human condition, way before "online" existed. For a new social media platform to succeed, it needs to capture a new vector in the identity expression space.
How do we define the "identity expression" space?
People like to express different facets of their identity (professional, athletic, personal, etc) in different mediums (audio, text, visual, musical, etc.) with different audiences (friends, family, public sphere, colleagues/collaborators, etc.).
Facets, mediums, and audiences are major dimensions of the identity expression space. There are other dimensions as well: short vs. long content; anonymous vs. not; ephemeral vs. not; paid vs. not; explicit vs. not, etc. etc.
Any Social Media platform can be plotted as a vector in this n-dimensional space (the origin point is you, your full raw identity). Facebook is the OG player in the space, the "catch all" platform (Facebook more or less lets you post whatever, to whomever) that occupies a bunch of vectors reasonably well. Other players tend to be more specialized.
To put it in concrete terms, look at how the same individual can express their identity across a dozen different vectors concurrently: