I've seen these before. Not sure it's the same, but in my case it was an elaborate way of follow-spam: they followed each other and a few levels deep there is a master node which tweets the spam link, all the others retweet it.
The bigger (and more effective) ones designed around a few rules, we found:
- accounts they "follow" are often a diversion, they are usually selected at random
- who they truly "follow" (i.e. actively listen to) is defined outside of Twitter
- they don't do "retweets" correctly, because that would also make connections visible; instead, they post messages fed to them externally as their own original tweets
- IFTTT plays a big role in simplifying automation while keeping the true relationships "invisible" to Twitter and people using Twitter APIs