Back in the 1980s all 3 major networks had their own election night teams that independently made the calls, based on independently collected data.
At some point in the 1990s I believe, several of them created a consortium to project the elections, because it was a very expensive process for each of them to do separately.
I'm not sure if they were granted an anti-trust exemption, or if it is just that no one ever complained about it.
Eventually the all joined.
This is a pretty decent article on the topic: How do networks call the election before all the votes are counted?
The Associated Press and the US’s five major news networks—ABC, CBS, CNN, Fox, and NBC—are all members of a consortium called the National Election Pool, which has provided election night information including the vote count, analysis, and projections since 2003.The real counting is of course done by County Clerks, County Election Officials, and in some places overseen by Federal Judges.