It sounds as if this team made several mistakes, not just one mistake. It's also not clear if the result of these mistakes was that there might be real damage to the spacecraft, or if the result was just wasted time and hours of confusion about why the spacecraft wouldn't start up.
The first mistake is they didn't realize that the multimeter was not only measuring, but it was also completing the circuit.
That sounds like a real bad idea. But if it was totally necessary to arrange it like that, then that multimeter should never have been touched.
That's not just one guy's error. It's at least two guys at fault, along with whoever is managing them, and whoever is in charge of the system that allows it.
The second mistake is with the break-out-box. They think he misdirected power wrongly into the spacecraft. Then they jump to the conclusion that has generated a power surge which has damaged the spacecraft, because it won't start up.
But they're not sure where the power surge went and what might be damaged. Anyhow they're wrong.
The reason the spacecraft won't start up is just because he took the multimeter out of the circuit before the accident.
I'm still sort of confused about what happened or if they ever really figured out what happened.
He said "Weeks of analyses followed on the RAT-Revolve motor H-bridge channel leading to detailed discussions of possible thin-film demetallization".
Does this mean that they decided that the misdirected power surge might have flowed into the RAT-Revolve motor H-bridge channel and damaged that?