I could be wrong but I think most people who went off tangent did post on-topic at first. I know I and at least one other did that. But then it's hard to not reply to other people's posts when I have something to say, sometimes. I did suggest a new thread should be created, which happens on occasion (they get "split" by a mod).
But yeah, it was kinda ridiculous.
On the other hand, if around 2/3 was off topic, that's still a few pages of genuine advice, which is more than a lot of threads get.