You are initializing in an existing Firebase project directory

You could use firebase init with flag --project <projectId>

The Firebase CLI will look in the current directory and all parent directories for a file called .firebaserc that defines which project is being used in this directory structure. If you run firebase init and encounter the message "You are initializing in an existing Firebase project directory", that means one of these .firebaserc files was found, and it's going to re-initialize this project.

If you no longer want the original project, just delete the .firebaserc file. Or, find another directory to run firebase init that isn't within another project's space.

Deleting .firebaserc did not work for me. I also had to delete firestore.json.

You need to delete .firebaserc and firebase.json file from the project directory. It works perfectly fine for me.