My guess is that it's the power management system for the servers that is accessible and using default passwords. Usually there are outlet groups or such that

My guess is that it's the power management system for the servers that is accessible and using default passwords. Usually there are outlet groups or such that can be controlled from an interface like the one in the screencap. The servers will talk to and trust the power system so that if there is a problem or outage they can be turned off. Being able to reboot is useful remote admin option. So like a lot hacks, primary access has been secured but someone forgot about the trusted secondary.