My note: MSA there is 15700 ft
I am not a pilot, nor am I familiar with the area. However, looking at google maps I can see that it is a short hop and, depending on runways in use, the majority portion of the flight is over water. A visual approach on Douala's easterly runway from the direction of Malabo would not constitute a problem flying at FL090. The problem presumably arose from the wx deviation and a possible loss of situational awareness.