Because this is not censorship. You're free to browse any defederated community. You're not censored, they're not censored. All the content is perfectly viewable on the fediverse.
Go join another instance. You can't enter somebody else's house and complain about how they don't want to invite the neighbor over as well. That's not censorship. Go to the neighbors house if you want to hang out with them.
But you've been explained this multiple times, so I'll leave it at this. Ignorance is not bliss.
Both. The text data is in the database of all instances that are federated. Your account credentials are only stored on the instance you're registered to.