My understanding of the business is limited. I did hear Patrick Whiteside speak at a dinner though last year, and from his description, it seemed like most of these shows are packaged up and sold by the studios of even the agency itself. So say the agency represents a good writer who has a new script and Reese Witherspoon suits the lead role, is also represented by the agency, and wants the work. The agency essentially will go pitch the script and likely cast to Netflix, Hulu, etc. so often Netflix isn’t the one actually the entire conception and implementation of the show. They are just the ones buying the rights to own it and distribute it.