A vessel the size of that merchant ship wouldn’t have to “ram” per se with a precise site in mind, just make contact. The mass and speed of the cargo ship would do the rest. Especially if, for some reason, the destroyer was a sitting duck.
Qs: Would the destroyer’s radar room receive transponder info from civilian shipping? If so, would a large civilian vessel approaching with its transponder either non-functioning or turned off be reason to consider the possibility of hostile intent?
Let’s suppose the captain of the ACX Crystal really wanted to ram the Fitzgerald. Wouldn’t he be moving ahead at flank speed? Combine that with the weight of the Crystal, and I’m thinking the the Fitzgerald would crumple, then sink.
And there doesn’t seem to be any scraping marks on the Fitzgerald. That seems to indicate that the did not Fitzgerald did not turn away.
My totally wild guess: the Crystal hit the Fitzgerald by accident, then went into full reverse. It might have even been in reverse when contact was made. Otherwise, how could the Fitzgerald survive?