All freshly written shows had to pass through one of the Big Three

Hello everyone. Do I correctly understand this sentence fragment in bold type? Does that means that the Big Three were checking all new tv programs (all fresh written shows)?

When the FOX Network began in 1986, cable television was still unavailable in most U.S. households, and the tiny handful of cable channels that did exist mostly ran niche programming, old movies, or reruns of network shows. Scripted original programming on cable was almost unheard of. With the exception of a few syndicated programs, all freshly written shows had to pass through one of the Big Three, and the networks had very definite ideas about what kind of programming they wanted from their entertainment divisions.