r/the_Donald was "quarantined" by the admins, so it cannot be discovered by users in the same way as other subreddits. That cut off a lot of the organic growth that you would normally see, and it cut off users who might normally see r/the_Donald on the r/all or r/popular wander in to comment/argue. People who are not already subscribers just no longer even see anything at all from r/the_Donald.