Some comments: - This is a really remarkable graph. I just didn't realize how thoroughly it was over for SO. It stuns me as much as when Encyclopædia Britannica stopped selling print versions a mere 9 years after the publication of Wikipedia, but at an even faster timescale. - I disagree with most comments that the brusque moderation is the cause of SO's problems, though it certainly didn't help. SO has had poor mode…
But the horrible moderation was in part a reason why many SO questions had no answers.
I am not saying poor moderation caused all of this, but it contributed negatively and many people were pissed at that and stopped using SO. It is not the only reason SO declined, but there are many reasons for SO failure after its peak days.