Pixar’s Cars movies have been the target of a lot of bizarre fan theories, with most of them centered around the fact that the universe clearly has no humans but still has evidence that humans once existed—i.e. door handles on the living cars, buildings and monuments that cars couldn’t build themselves, and the piles of skeletons that are always just off-camera in every scene. The movies themselves will probably never address the mysterious lack of humans, but it turns out that Jay Ward, the Creative Director of the Cars brand, has some theories of his own. This comes from Screen Crush, and though the piece makes it clear that it’s “not necessarily” official Pixar canon, Ward himself has an extremely dark idea for where the humans went:
If you think about this, we have autonomous car technology coming in right now. It’s getting to the point where you can sit back in the car and it drives itself. Imagine in the near-future when the cars keep getting smarter and smarter and after one day they just go, “Why do we need human beings anymore? They’re just slowing us down. It’s just extra weight, let’s get rid of them.” But the car takes on the personality of the last person who drove it. Whoa. There you go.
There are two distinct ideas here. One is that the Cars cars took on the personality of the last person who drove them, which is kind of funny and clever, and the other is that the humans were all murdered by the cars when they realized that they no longer needed us. As Screen Crush notes, that’s basically Terminator, and it means there was probably a Judgment Day-esque event where all of the cars systematically crushed every human and took over the planet.