Can not override `replicas` of deployment k8s – Debian

I have met a problem like this:

Firstly, I using helm to create a release nginx:

helm upgrade --install --namespace test nginx bitnami/nginx --debug

LAST DEPLOYED: Wed Jul 22 15:17:50 2020
NAMESPACE: test
STATUS: DEPLOYED

RESOURCES:
==> v1/ConfigMap
NAME                DATA  AGE
nginx-server-block  1     2s

==> v1/Deployment
NAME   READY  UP-TO-DATE  AVAILABLE  AGE
nginx  0/1    1           0          2s

==> v1/Pod(related)
NAME                    READY  STATUS             RESTARTS  AGE
nginx-6bcbfcd548-kdf4x  0/1    ContainerCreating  0         1s

==> v1/Service
NAME   TYPE          CLUSTER-IP    EXTERNAL-IP  PORT(S)                     AGE
nginx  LoadBalancer  10.219.6.148  <pending>    80:30811/TCP,443:31260/TCP  2s


NOTES:
Get the NGINX URL:

  NOTE: It may take a few minutes for the LoadBalancer IP to be available.
        Watch the status with: 'kubectl get svc --namespace test -w nginx'

  export SERVICE_IP=$(kubectl get svc --namespace test nginx --template "{{ range (index .status.loadBalancer.ingress 0) }}{{.}}{{ end }}")
  echo "NGINX URL: http://$SERVICE_IP/"

K8s only create a deployment with 1 pods:

# Source: nginx/templates/deployment.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx
  labels:
    app.kubernetes.io/name: nginx
    helm.sh/chart: nginx-6.0.2
    app.kubernetes.io/instance: nginx
    app.kubernetes.io/managed-by: Tiller
spec:
  selector:
    matchLabels:
      app.kubernetes.io/name: nginx
      app.kubernetes.io/instance: nginx
  replicas: 1
  ...

Secondly, I using kubectl command to edit the deployment to scaling up to 2 pods

kubectl -n test  edit deployment nginx

# Please edit the object below. Lines beginning with a '#' will be ignored,
# and an empty file will abort the edit. If an error occurs while saving this file will be
# reopened with the relevant failures.
#
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
  annotations:
    deployment.kubernetes.io/revision: "1"
  creationTimestamp: "2020-07-22T08:17:51Z"
  generation: 1
  labels:
    app.kubernetes.io/instance: nginx
    app.kubernetes.io/managed-by: Tiller
    app.kubernetes.io/name: nginx
    helm.sh/chart: nginx-6.0.2
  name: nginx
  namespace: test
  resourceVersion: "128636260"
  selfLink: /apis/extensions/v1beta1/namespaces/test/deployments/nginx
  uid: d63b0f05-cbf3-11ea-99d5-42010a8a00f1
spec:
  progressDeadlineSeconds: 600
  replicas: 2
  ...

And i save this, check status to see the deployment has scaled up to 2 pods:

kubectl -n test get deployment

NAME    READY   UP-TO-DATE   AVAILABLE   AGE
nginx   2/2     2            2           7m50s

Finally, I using helm to upgrade release, as expected, helm will override the deployment to 1 pod like first step but in for now, the deployment will keep the values replicas: 2 even you set the values (in values.yaml file of helm) to any number.
I have using option --recreate-pods of helm command:

helm upgrade --install --namespace test nginx bitnami/nginx --debug --recreate-pods
Release "nginx" has been upgraded. Happy Helming!
LAST DEPLOYED: Wed Jul 22 15:31:24 2020
NAMESPACE: test
STATUS: DEPLOYED

RESOURCES:
==> v1/ConfigMap
NAME                DATA  AGE
nginx-server-block  1     13m

==> v1/Deployment
NAME   READY  UP-TO-DATE  AVAILABLE  AGE
nginx  0/2    2           0          13m

==> v1/Pod(related)
NAME                    READY  STATUS             RESTARTS  AGE
nginx-6bcbfcd548-b4bfs  0/1    ContainerCreating  0         1s
nginx-6bcbfcd548-bzhf2  0/1    ContainerCreating  0         1s
nginx-6bcbfcd548-kdf4x  0/1    Terminating        0         13m
nginx-6bcbfcd548-xfxbv  1/1    Terminating        0         6m16s

==> v1/Service
NAME   TYPE          CLUSTER-IP    EXTERNAL-IP    PORT(S)                     AGE
nginx  LoadBalancer  10.219.6.148  34.82.120.134  80:30811/TCP,443:31260/TCP  13m


NOTES:
Get the NGINX URL:

  NOTE: It may take a few minutes for the LoadBalancer IP to be available.
        Watch the status with: 'kubectl get svc --namespace test -w nginx'

  export SERVICE_IP=$(kubectl get svc --namespace test nginx --template "{{ range (index .status.loadBalancer.ingress 0) }}{{.}}{{ end }}")
  echo "NGINX URL: http://$SERVICE_IP/"

Result: after I edit the replicas in deployment manually, I can not use helm to override this values replicas, but I still can change the images and etc, … only replicas will not change
I have run --debug and helm still create the deployment with replicas: 1

# Source: nginx/templates/deployment.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx
  labels:
    app.kubernetes.io/name: nginx
    helm.sh/chart: nginx-6.0.2
    app.kubernetes.io/instance: nginx
    app.kubernetes.io/managed-by: Tiller
spec:
  selector:
    matchLabels:
      app.kubernetes.io/name: nginx
      app.kubernetes.io/instance: nginx
  replicas: 1
  template:
    metadata:
      labels:
        app.kubernetes.io/name: nginx
        helm.sh/chart: nginx-6.0.2
        app.kubernetes.io/instance: nginx
        app.kubernetes.io/managed-by: Tiller
    spec:      
      containers:
        - name: nginx
          image: docker.io/bitnami/nginx:1.19.1-debian-10-r0
          imagePullPolicy: "IfNotPresent"
          ports:
            - name: http
              containerPort: 8080
            
          livenessProbe:
            failureThreshold: 6
            initialDelaySeconds: 30
            tcpSocket:
              port: http
            timeoutSeconds: 5
            
          readinessProbe:
            initialDelaySeconds: 5
            periodSeconds: 5
            tcpSocket:
              port: http
            timeoutSeconds: 3
            
          resources:
            limits: {}
            requests: {}
            
          volumeMounts:
            - name: nginx-server-block-paths
              mountPath: /opt/bitnami/nginx/conf/server_blocks
      volumes:
        - name: nginx-server-block-paths
          configMap:
            name: nginx-server-block
            items:
              - key: server-blocks-paths.conf
                path: server-blocks-paths.conf

But the k8s deployment will keep the values replicas the same like the edit manual once replicas: 2

As far as I know, the output of helm command is create k8s yaml file, Why I can not use helm to override the specific values replicas in this case?

Tks in advance!!!

P/S: I just want to know what is behavior here, Tks

Helm version

Client: &version.Version{SemVer:"v2.13.1", GitCommit:"618447cbf203d147601b4b9bd7f8c37a5d39fbb4", GitTreeState:"clean"}
Server: &version.Version{SemVer:"v2.13.0", GitCommit:"79d07943b03aea2b76c12644b4b54733bc5958d6", GitTreeState:"clean"}