[jfengel]

The answer is "other users". The value of a social media rises with the square of the number of users. If none of your friends are on it, you probably won't join.

The technology is easily replicated, so there are lots of alternatives. But no one alternative is overwhelmingly obvious, so the number of users on each is small. Even if half of Twitter's users fled, the sum of other sites' values will still be much smaller than the remaining half.

It may be that a Bluesky or Threads or some such will eventually reach a threshold -- especially if they can be inter-connected and benefit from the increased size. But that only happens of X is really unpleasant -- which apparently, it is.