No authentication required after Configuration of Keyfile in Replica Sets (GKE)

I installed Mongo in GKE and now I’m trying to secure it.
I followed this guide

(I know it’s not for containers)
the problem was mongod.conf does not exists. The only configuration file present is mongod.conf.orig and
I edited this but mongo continue to grant access without user’s password.

Maybe I should have copied mogod.conf.orig to mongod.conf, shouldn’t I?

Can somebody help me understand if can be this the problem?