[Note: This piece contains many spoilers for Nier: Automata's structure and mechanics, though plot spoilers are kept to a minimum. There are still some though, so if you're already a Nier convert and know you're going to play Automata beyond the credits, you may want to avert your eyes.]
First things first: you don't need to play four times to get its true ending. That's a myth - one based on the first Nier that actually did require such a task. No, instead Nier: Automata is comprised of four different campaigns, which is a very different situation.
The funny thing is that Nier: Automata doesn't advertise three of these campaigns. It politely requests that players stick around after the credits to unveil the full story (really, there actually is a post-credits message suggesting this), but it doesn't outright tell you what you'll see if you keep playing, just as Konami audaciously didn't inform anyone about Castlevania: Symphony of the Night's second castle upon release. The point is for the player to discover Nier: Automata's secret second act. And then its third act. And its fourth.