LinkedIn?

I joined three Zumba-related groups at LinkedIn. One is called ZIN-Zumba Instructors Network (as of today, 823 members):


Another is called Zumba Instructor Network (497 members):


The biggest group is called Zumba Community (1027) members):


Now I understand that the Zumba community is bigger than ZIN, so no surprises here. But what is the point of both ZIN-Zumba Instructors Network and simply Zumba Instructors Network? As far as I can see, both groups run discussions in parallel without much interaction with each other. For instance, what portable sound system is better. (That’s what I am looking into right now.) It is interesting to see different consensus opinions emerging on the same topic though.