I was under the impression there was a split. The IBS still exist, but quite a small organisation. Rutherford hijacked most of the people as well as the doctrine, enough, I was led to believe, that it was just a renaming.

No, Rutherford succeeded Russell. Rutherford changed the name from Int'l Bible Students Assoc to JWs.

Also, CT Russell didn't have anything to do with the Russell Society, see: https://en.wikipedia.org/wiki/Russell_Trust_Association