They're almost sort of opposites? Firekube is the Kube control plane running on lightweight Firecracker-powered VMs. On the other hand, Kata Containers is a CRI runtime (like containerd or CRIO) that allows Kubernetes to schedule containers to start through Kata (which then allows the container to run via Firecracker or Qemu, IIUC). But also, I think in practice everyone uses Containerd/CRIO and then configure them to pass untrusted workloads onto Kata.

I'm not sure what to think of how all of this ended up.