In the deployment of a two-node cluster at a remote branch office, the presence of a Witness VM is essential to manage the cluster quorum and data integrity in case one of the nodes fails or becomes unreachable. The Witness VM acts as an external arbitrator that helps prevent data unavailability and split-brain scenarios in a situation where the cluster nodes cannot communicate with each other. This configuration is necessary because with only two nodes, there isn't a third node to maintain quorum natively.References: Nutanix Bible, Nutanix University