That explains a lot.
If that little AIS box , mounted away from the radar, with a list of targets on a 4” screen to scroll through is all they had, no wonder they didn’t know what the tanker was.
AIS without a display on the radar and chart plotter is close to useless. The most useful feature of AIS is having the names and predictor lines of all the vessels as a true motion display super imposed over the chart.
On the radar, the little AIS triangles next to targets tell you at a glance that it’s a ship. Selecting the target instantly provides the critical information about the target.
The failure to have the AIS receiver interfaced with the radar is negligence per se. Its as bad as turning the AIS transmitter off.
Attempting to blame the Spanish Shipyard for the ship sinking is laughable.