So fact checkers were invented.No, fact checkers existed for decades before social media. Even before the internet.
I've worked in newsrooms as recently as the 1990's where there were fact checkers. Usually nice people with many very large, expensive books to double-check things.
But when the media companies became beholden to Wall Street instead of the public, the fact checking departments were the first people cut in the name of "maximizing shareholder value."
That was followed by consultants ( * cough * Broadcast Image Group * cough * ) who constantly pushed for more and more "breaking news" hype and convinced news managers that it was more important to be first than to be right. The public ate it up and it became a feedback loop.
I could go on, but this isn't the place for it.