For months, the entire entertainment industry has monomaniacally focused on how to return to work amid the coronavirus pandemic. Reams of health and safety protocols have dictated everything from proper PPE attire to testing schedules to how many people can be on a set, and by July and August, a small handful of major productions — like “The Matrix 4” and “Jurassic World: Dominion” — began to put those guidelines through their paces. While a few people have tested positive, barely any outbreaks have been reported, and no productions have had to stop completely. It started to seem like maybe Hollywood’s full pipeline could finally start flowing again.