In the last couple of weeks, it was proven that these so-called "fact checkers" are paid per "fact check" by IFCN with cash funneled from Facebook, Twitter 1.5 (see previous post) and many other leftist sites that use them.
Thanks to Elon Musk for making the contract that Twitter 1.5 had with IFCN public. It was confirmed by a "source" at Facebook that it's the same contract FB has with IFCN.
Even though I don't usually trust "sources", it makes sense that everyone has the same contract (money amounts based on size) since "big tech" colluded on most things, so it would be nearly impossible for them not to find out what the others's contracts were.