Kubernetes doesn't compete with CoreOS except in that both CoreOS and Kubernetes have their own schedulers (fleet and the k8s API server).
However, fleet is designed to be relatively simple, and can be used to deploy 'services' (as in systemd services), while kubernetes is more oriented around deploying 'apps', and provides a much higher abstraction that makes discovery, etc easier.
However, fleet is designed to be relatively simple, and can be used to deploy 'services' (as in systemd services), while kubernetes is more oriented around deploying 'apps', and provides a much higher abstraction that makes discovery, etc easier.