When I was in the Navy, there would be multiple people on the bridge--the place where the ship is driven. On this size ship, there would've been a minimum of one officer, a helmsman, a quartermaster, a messenger, and likely some lookouts on both sides of the bridge. Additionally, a lookout may have been posted on the aft part of the ship.
The bridge would've had access to at last one radar unit, as well as a tactical display that's fed from all the sensors. This ship is equipped with Aegis, in which all contacts--surface, air and subsurface can be fed through a number of ways.
In addition to the bridge personnel, there would've been watchstanders in the Combat Information Center, also looking at surface and air radars. It's very likely that sonar operators in Sonar Control would've detected this large (and loud) vessel as well. I have no doubt that all of those sensors detected a large surface contact, close abroad. The surface watchstanders in CIC would've undoubtedly been in contact with the bridge, calling out distances: "1000 yards, 500 yards..." etc.
Assuming detection by the Fitzgerald, the first question that comes to mind is, why did they place themselves in extremis by remaining that close? This type of ship is highly maneuverable, and should've given a wide berth to the container ship. There was nothing to be gained by challenging the much larger vessel.
Another question I have is did the bridge personnel on either ship contact the other via bridge-to-bridge radio or flashing signal lights? Was there some kind of misunderstanding between such communication, if it occurred?
Another question is about other vessels in the area. I understand this is a highly-congested shipping lane. Did the container vessel (or the destroyer) have to turn unexpectedly to avoid another ship? Within a narrow channel, that might be a concern; farther out at sea, there shouldn't have been anything forcing the Fitzgerald to take such a drastic action as to turn in front of the ACX Crystal.
While the Navy doesn't employ "black boxes" like they do on civilian aircraft, there should be ample logs showing the exact location of the vessel. They will also be able to reconstruct where all the surface vessels were, including all their headings and speeds. There will be logs kept on the bridge of the Fitzgerald--the log book will be most interesting to read (and likely revealing), because it will include all the navigational commands given, and any reports from the lookouts. CIC Watch logs will also be useful.
My initial assessment is that this is an accident that need not have happened. It's certainly an investigation that should be very straightforward in evidence and very clear about how things happened. It's very likely that higher-ups already have a good idea of what happened, but will wait for a full report before disclosing anything.
Looking at photos of damage to both vessels and knowing that “Fitz” suffered below waterline damage (prolly from bulbous bow of freighter) I wonder how long both vessels were in physical contact. Could the destroyer have been pinned to the bow of the freighter for a time,caught between bulbous bow, prow and force of water from freighter’s headway?