A night letdown over water in poor weather is a straightforward process which the crew will have practiced many times, They have a forward looking radar to check the area is clear of obstacles and they will let down to a predetermined height and engage the Trans Down mode for the autopilot - this will take them from a specified height (I don't know what their SOPS are) to a defined Rad Alt height over the water - hopefully VMC beneath the weather.
There will be several cross checks to make sure the AP is performing correctly as well as height and speed calls and crosschecks between the pilots and the rearcrew won't be twiddling their thumbs while this is going on either - possibly using the FLIR and or/monitoring the radar.
The crew will have also discussed the actions if they don't get visual.
It should be a pretty automated process unless the crew elect to manually fly the cyclic program in order to manoeuvre to keep clear of radar contacts or if a part of the AP system fails.
For CFIT to occur in this process would be unlikely unless they thought they were visual under the weather and disengaged the AP letdown modes - even then they would probably still retain the Rad Alt hold - in trying to transfer from instruments to NVD it is possible they lost visual references but this is the sort of thing they train for.
Once established in an overwater hover with everything coupled, they would discuss how to get to the LS and use the AP systems to achieve this.
With 2 pilots and a fully serviceable AP with all the bells and whistles, disorientation leading to CFIT is unlikely but not impossible.
There are many system failures, especially at crucial stages of flight low level over the water which could overwhelm the crew who are already working quite hard and are probably a little fatigued since it was 01:30 and any major catastrophic failure would be impossible to recover from at such low altitude in poor conditions.
We will eventually discover the sequence of events and possibly the cause or causes of the accident but not until the CVFDR is recovered and analysed.
Yes, it is 'just' another accident but when those who are required to fly in conditions when most would stop in order to rescue others and are killed in the course of their duties, it is doubly tragic.