This is a stupid article. You need Linux to run Kubernetes, one (and the way it's configured is even more important given the thinner security barrier between containers and their host), and, two, not every workload will be suitable for containers or Kubernetes.
This is really pushing it now. Kubernetes is great for numerous applications, but it is far from necessary in many applications too.
Could someone help explain to me how kubernetes is actually an operating system?
I thought it had something to do with containers.
Guessing my OS, they mean just like back when the web was taking over and the web was the os, taking over from Windows. In this case, you don't build specifically for Linux, but for Kubernetes and it can be deployed anywhere, including Windows, eventually.