"This isn't Matlock"
Sure, he's responsible because something broke. I'll agree that when a valve breaks loose, its his job to respond to it. But its not his fault that the valve break if it was a hidden, unknown design flaw - the Navy won't can a unique asset like a sub captain just because people on the internet think they should.
More things we don't know: maybe the Captain's expertise saved all their lives when they ran aground? Maybe he'll be given a medal for rising to the occasion? You don't know enough about the situation.
Yup.... we can't condemn the Captain , we don't have all the facts ( and probably will not get all the facts ). If it was a unexpected loss of power or a design flaw in the sub, why should we blame the captain ? Even if they were using sonar, it could have been a large rock or something like that, that could have been affected by a earthquake.