Yup. I am currently designing the network .....
And there you have, at least part, of it.
Systems are not just the sum of its components. You can have a great system but, if they aren't designed, installed or maintained properly you have a pile of useless. FTR, my role is the integrator of the various stuffs, like Network, DR, Server, Service, etc etc
Go on, another anecdote (dating back about 15 years). Another major corp with highly redundant highly secure systems lost complete contact with their, erm, contact centre. I happened to be there and got involved. Turned out that the dual redundant inbound circuit terminations when installed had not only been plugged in to the same dual socket, but a wall socket instead of a cabinet socket had been chosen. And someone had plugged in a kettle. That was all it needed.