[pdonis]

> How common are scenarios where there are multiple ships within visual distance?

In a main shipping channel near a busy port? Very common.

> It's hard for me to understand how they didn't realize they weren't getting useful data from that radar and switch their primary navigation driver to the other radars, lookouts, the commercial position broadcasting system, or the infrared camera, all of which seemingly worked.

Or the old standby, the Mark One eyeball. As I commented elsewhere upthread, the thing that jumped out at me was not having a lookout on both bridge wings (port and starboard). Even with a ship that's shorthanded, that's the last place you should give up personnel, especially when navigating in a crowded shipping channel at night. They should have made up the shortfall from somewhere else.