Taken directly from the Nomad website[1]:

Kubernetes and Nomad support similar core use cases for application deployment and management, but they differ in a few key ways.

Kubernetes aims to provide all the features needed to run Docker-based applications including cluster management, scheduling, service discovery, monitoring, secrets management and more.

Nomad only aims to focus on cluster management and scheduling and is designed with the Unix philosophy of having a small scope while composing with tools like Consul for service discovery/service mesh and Vault for secret management.

Compare Kubernetes Pods and Deployments to Nomad, and the full Kubernetes ecosystem to the full Hashicorp ecosystem please.

IMHO, Vault and Consul are very hard to operate correctly, at least as hard as a Kubernetes cluster on-premise (managed Kubernetes does not count).

[1] - https://www.nomadproject.io/docs/nomad-vs-kubernetes