How can you plan for things occurring out of your control? CF engineers are people as well. Things like this happen and there will be learnings to take out of it (like how to fail over faster)
Circulating a MOP(method of procedure) for data center maintenance among all stakeholder is pretty standard. The purpose of the MOPS is so that everyone can vet the plan(roll forward and roll back)and identify the risks.
As Matthew said on Twitter, this isn't the kind of mistake that happens twice. But for those of us who do operational work, it's easy to see how this happens once. Bit rot in a cab, work orders from someone who didn't know about the legacy patch panel or assumed too much in their instructions and a catastrophe. From now on, photos for every smart hands will probably be a part of the prep-procedure.
That's a pretty odd and flimsy argument that I can't know what I'm talking about if I hold an opinion that differs from your own. I have years of experience with this particular space. Had a MOP been circulated and the maintenance plan properly vetted then the need for visual confirmation because of "legacy patch panel" and "bit rot in cab" would have been identified. Further you never unplug a cable unless you first verify what the ends of the cable are connected to. As I mentioned this is "datacenter operations 101" stuff. This is not some new startup, this a publicly traded company who has been in the game for a decade now.
If this failure was so easy to avoid, it would have been avoided. It was the result of a combination of failures, as all failures in highly-available systems are. It was a failure in bitrot, in planning, in execution, in communication, in reluctance to failover due to a concern about failing back, etc.
That said, like Matthew said, this is the kind of failure that happens once.