Scheduling an airline flight into Moroni at night is a very dangerous thing to do. The risks involved are too high and the services available are very minimal. The non-precision app at night is a ridiculously difficult approach in good weather, with turbulence and strong winds it has always been an accident waiting to happen.
The Yemenia pilots operate out of very difficult airports in tough conditions on a daily basis, Sanaa their home base can be a very tough place to operate a wide body jet. I would not assume that their pilots skills were lacking.
Any pilot flying that approach in bad weather at night would have a much higher risk of dying than is acceptable.
The airline I flew there with pulled out of Moroni 5 or 6 years ago because of those dangers, thankfully!
What ever the cause of this crash, hopefully night flights into that place will be stopped by all airlines.