These board of inquiries are harsh by nature, and intentionally so.
When an officer takes command of a vessel, he is in charge of United States territory, and there is a lot of responsibility that goes along with that, apart from the possibility of damaging the vessel due to incompetency or accident.
They know that when they take command, and when something happens, there is merciless armchair quarterbacking. That is by design.
If you are the Captain of a US Navy vessel, then you know in advance, you are not going to get any mercy, forbearance, or consideration from one of these boards. You just don’t expect it.
It does occasionally happen, though. Chester Nimitz as a young Ensign, ran the USS Panay (not the same one the Japanese destroyed on the Yangtze River) aground in the Philippines and appeared before a board of inquiry. He argued his case so convincingly (that the charts were outdated) that they actually let him off. Very rare.
It did have an effect later in his career on his conduct as a Captain and Admiral, where he was known to show leniency for first time offenders. One of his favorite sayings was “Every dog deserves a second bite...”
As a former naval officer, I approve of this seemingly harsh policy. If you are by definition at fault, you do a lot more to prevent anything preventable. Note: I never worked for anyone as forgiving as Admiral Nimitz, but I’m okay with the hard cases I worked for.
Remember Bull Halsey? He was lucky that was in the time of war and they needed him.