You've picked up on the tail end of the history there, Barmaid.
Chatterbank was actually created precisely because B&S was full of irrelevant trivia (together with a great deal of abuse as well), meaning that anyone who was, say, concerned about a parent's cancer would be extremely unlikely to post a serious question there.
So, as intended, all of the trivial (and/or abusive) posts moved to CB. However things then got so out of hand that CB was shut down. The result of that, unsurprisingly, was simply that all of the trivial/nasty stuff simply moved back to B&S again.
It was at that stage the Eds realised that, since they couldn't monitor the site 24 hours per day, it was necessary to appoint some moderators from among AB's members. Once that had been done, CB was reopened and B&S returned to being a place solely for serious posts.