Answer
Because the entire desired state is in Git, recovering a cluster means installing ArgoCD and pointing it at the same Git repos; it rebuilds all applications to match. This makes clusters reproducible and reduces recovery time. Combined with backups of stateful data and cluster-level bootstrap (App of Apps), whole environments can be recreated declaratively.
Real-world example After losing a cluster, the team provisions a new one, installs ArgoCD, applies the root app, and the platform rebuilds from Git.