Why would they want to take over the world?
Why indeed. But the Morris Internet Worm didn't want to take over the internet, poor fledgling little thing that it was back in 1988. But it did, at least until the real intelligences noticed. And those blue-green algae didn't want to poison the world with oxygen (one suspects that producing oxygen had more to do with fending off ancient bacteria), but they did. Those wasps who shed their wings and developed huge insect societies 200 megayears ago didn't want to take over, but they did.
You don't need intent. You just need ability.