Thank you very much for the complete report, I congratulate you because this information is not always shared.
And I remember that a similar incident happened in another datacenter contabo.com and this time it happened with a lightning strike in the cooling system of the datacenter. On that occasion the alarms did not go off before because when the servers started to warm up, everything was automatically shut down and the entire company is completely off the grid.
https://contabo.com/blog/nuremberg-incident-root-cause-analysis/