Why is the original pod restarted when increasing the number of Kafka replicas instead of directly adding new pods

[AllenZMC]

Why is the original pod restarted when increasing the number of Kafka replicas instead of directly adding new pods ?

apiVersion: kafka.strimzi.io/v1beta1
kind: Kafka
metadata:
  name: my-cluster
spec:
  kafka:
    version: 2.7.0
    replicas: 3

Will it affect the consumption of messages from topics?

[scholzj]

Discussed in https://cloud-native.slack.com/archives/CMH3Q3SNP/p1611063949086100