This keeps happening because it works. But why does it work? Why isn't there blowback?
This has always been the case.
However, the more interesting thing going on is that we have never had to reckon with this problem anywhere near as much as we do now, since the barrier to creating fakes has been reduced from "skilled, motivated software user" to "all five billion humans who can write".
Edit: I think this comment is neutral enough to stand even under the new information that this might have been a cries-wolf situation, but I am acknowledging the fact.
Simply provide the new information, rather than snarkily implying that the parent is some kind of asshole. Save that for the normal internet.
It's pretty obvious the OP is a thinly veiled attack at whoever believed the "lie", dressed up as a question. The only saving grace is that the wording was so ambiguous that regardless of whether it was the debunking or counter-debunking that was correct, the comment would still be applicable.
edit: the story was retracted so the "people manipulated with lies" are the people who believed oregon journalism project?