All this FMC/GPS stuff is true .. but we are missing a fundamental truth. They did not brief for the visual .. it was the all time classic which features in so many safety reports .. "we will shoot the visual".
If you are downwind with everything looking good and you are offered the visual and you have not briefed it - simple ... do not do it! You might save max 2 minutes flight time by doing the visual but it takes far less than 2 minutes for everything to go badly wrong.
This was a failure of SOPs or a failure to abide by SOPs and very very bad airmanship that came very very close to a lot of people dying.