Apache Flink job is not scheduled on multiple TaskManagers in Kubernetes (replicas)
The first task manager has enough slots (10) to fully satisfy the requirements of your job.
The scheduler's default behavior is to fully utilize one task manager's slots before using slots from another task manager. If instead you would prefer that Flink spread out the workload across all available task managers, set cluster.evenly-spread-out-slots: true in flink-conf.yaml. (This option was added in Flink 1.10 to recreate a scheduling behavior similar to what was the default before Flink 1.5.)