'brittle' here, I interpret as: not simple to restore, the knowledge to get them stood up again is brittle. A bus factor of one, to get back in SWE parlance. I

'brittle' here, I interpret as: not simple to restore, the knowledge to get them stood up again is brittle. A bus factor of one, to get back in SWE parlance. If that factory burns down or a forklift crashes into the machine, it might be gone with no chance of recovery because the knowledge is gone.