These are among many questions that need to be answered. There are multiple, redundant systems onboard the Navy ship, both electronic and personnel that should've detected the cargo ship and evaded it, but these all failed. Some Freepers have offered reasonable explanations, and others some explanations that defy logic and seamanship. Data will be available in both electronic, written, and by oral testimony. All of this should be neatly summarized in the final report, and a clear picture should be available.
The one elephant in the room everyone is ignoring and not talking about, including the USN, is the OOD......why. Was it a mooselimb? a female with hormone issues, or a guy taking a nap or watching porn on his i phone? The captain was asleep at 2:30 am in the smashed up quarters in the pic, so we know he’s innocent. Everything points to the OOD.
My guess as to what happened is that there were initially two tankers in the picture (fact) and that the other tanker (the Wan Hai, I believe) was the perceived threat to the Fitzgerald. In avoiding the Wan Hai, the crew of the Fitzgerald set a course across the bow of the second tanker, the Crystal, which went undetected by the bridge until the collision, or was detected so close to the time of the collision that they couldn’t take action to avoid it.
It’s also possible that someone on board relayed the existence of the Crystal and the approaching threat but their message was interpreted as referring to the Wan Hai, which the Fitzgerald was already avoiding. This is speculation, of course, but the potential role of the Wan Hai has gotten little notice and is, I think, worth considering.
Something similar happened to the Porter years ago. It was in the process of avoiding one tanker when it was surprised by the existence of a second one, and collided with it.