With all three of them relieved I’m guessing this was not an “unknown” seamount.
I'm former Army, but in my experience, the entire chain of command is relieved only when there's a major eff up.
I was an Air Defense Artillery officer, in a composite Chaparral/Vulcan battalion in Germany...short range AD. A few miles off base was a Nike-Hercules battery, that had "special" weapons. I got to know the officers there quite well, as one of my "extra duties" was to lead a 40 man reserve force should they be attacked by terrorists or other bad guys.
At least every six months, they had a Nuclear Surety Inspection. Their outbriefings were attended by the ENTIRE chain of command of 32nd AADCOM, to include the Deputy CG flying in from Darmstadt. I was there, too, with my Battery Commander, due to my reserve force's participation...and yes, we were evaluated too.
There was one battery that flunked their NSI...the entire chain of command, up to and including the Group Commander (full bird colonel), were relieved on the spot. So yeah, pucker factor was high in the moments before the outbriefing.
One of my most memorable days of my undistinguished military career came during one of those NSIs. I was in high spirits when we arrived with my reserve force 30 minutes prior to mission time. However, the chief evaluator, a prickly LT Colonel started give me a ration of fecal matter: "you're only five miles away, how come it took you 3 1/2 hours to get here?"
Simple answer: we had to assemble 40 men, get the right equipment, and train them for the mission before we left our motor pool. My guys were air defenders and mechanics, who hadn't seen small unit infantry tactics since Basic Training.
I told the LTC, "I was giving my soldiers the extra training they needed to accomplish whatever mission they were given." He didn't like my answer, but I wasn't backing down.
As we fast forward to the outbriefing, that was the only negative comment he could come up with. Needless to say, I was one pissed off LT, and the officers in the other battery were chuckling, the pressure was off them.
After the evaluation team left, our DCG, a one star, goes up to the podium for congratulatory remarks. First thing he does is points his finger at me and says, "LT NHN, I will take that hit for you. Anytime you want to give your soldiers extra training, you have my express permission." That, in my opinion, was VERY cool...lol.
“With all three of them relieved I’m guessing this was not an “unknown” seamount.”
Has me suspecting they weren’t fired for the collision but for actions taken AFTER the collision. Maybe tried to shade what happened?