What made everybody move from a corporate social media platform to another corporate social media platform instead of the fediverse?
After all, the Fediverse and Activitypub is much more mature than Bluesky and the copycat AT protocol or Threads and … whatever they use.
Sometimes the identity of the messenger is important.
Twitter was super easy to set up with the API to periodically tweet the output of some automated script: a weather forecast, a public safety alert, an air quality alert, a traffic advisory, a sports score, a news headline, etc.
These are the types of messages that you’d want to subscribe to the actual identity, and maybe even be able to forward to others (aka retweeting) without compromising the identity verification inherent in the system.
Twitter was an important service, and that’s why there are so many contenders trying to replace at least part of the experience.