The audience cannot see how many versions were necessary to make a line feel inevitable.

A line that feels inevitable was almost never the first one. It reached that quality by being tried and rejected in many forms until one arrived that seemed as though it could not have been otherwise. Inevitability is an effect that gets manufactured, and the manufacturing is precisely what the finished version hides.

This matters when you are stuck. If your first phrasing feels wrong, that is not a signal about your ability but a normal position in the process. Write the version you dislike, then the next. And when you admire something that seems effortless, resist concluding that its maker simply saw it clearly. They mostly saw it badly first, repeatedly.