My second point is that, in a setup of any complexity, a black start is nontrivial. You have a network, with routes, DNS config, maybe VLANs, maybe a whole SDN. If that’s down because the machines running it are trying to pull their own configuration over the network, it won’t come back up. You can get pretty far into the weeds with situations like this.

Facebook supposedly got locked out of their own datacenter due to a network outage preventing the access control system from accessing whatever service it needed to allow anyone to open the door.