why kubectl command not working for describe pod
You've not specified the namespace in your describe pod command.
You did kubectl get all -n minio-operator, which gets all resources in the minio-operator namespace, but your kubectl describe has no namespace, so it's looking in the default namespace for a pod that isn't there.
kubectl describe po -n minio-operator <pod name> should work OK.
Most operations in kubernetes are namespaced, so will require the -n <namespace> argument