So why did no member of the crew notice a honking great lighthouse shining at them?
Even in IMC, when you get close to it, it will light up the inside of the cloud.
When you're VMC and co-alt, it should be shining right into the cockpit, and those things are BRIGHT!
Lighthouse service says it was on at the time (as in, remotely switched on), but was it actually working? Why would it not have been noticed? The first anyone seems to know of an obstacle (despite the Co-Pilot having Radar displayed in GMAP mode on his MFD), is when the crew in back ask for a right turn.
The 701 radar has pretty good ground mapping. And it will do it to a close enough range that objects don't disappear from the display until you're nearly on top of them (unlike the 660 radar), so why no visual of the light and no radar sighting of a b***dy great rock in front of you?