I know this question has been discussed, but I can't find the topic I was just looking at, so...
One thing about this is that the other posters here didn't mention, that I noticed anyway, that there was this member of the GB in the 40s and early 50s (but possibly during Rutherford) who was at odds with Rutherford or Knorr, and they wanted to do away with them, so they accused (falsely) that person, then they declared that the punishment for that sin was something they invented, or at least Once iteration of, what we know as the modern disfellowshipping practice among JWs.
So, that is why they invented that doctrine; they