Datastore started filling up with no changes being made in the vSAN cluster.
ESXi 8.0
vCenter 8.0
vSphere Replication 8.8
vSphere Replication was configured with a high retention policy which keeps a high number of snapshots for Multiple Point in Time (MPIT) recovery.
This configuration is fine if your environment or policies require this. Be sure to follow the Best Practices for Using and Configuring vSphere Replication.
Lower the retention policy which decreases the number of Multiple Point in Time (MPIT) snapshots. This should bring the storage usage back down.