This is clearly a case of pilot error and they should've known/done better, tragic but totally preventable.
Here' some insight from my 6 months flying the MC-12 in Afghanistan. No offense to anyone here, but IME flying a tactical ISR platform like the MC-12 has little in common with flying KA350's. It's not uncommon to be very very busy in the MC-12. The mission commander is typically working on a computer (with the screen mounted over the top of the basic pilot displays). I used to look across at the co-pilot (who sits in the left seat) displays to make sure we weren't doing anything crazy. You can also see the backup easily even with the laptop screen up. Typically the MC is working on as many as 6 operations, coordinating with 10 or 12 different agencies and monitoring what the sensor operator is doing while listening to/talking on as many as 7 radios.
The co-pilot also serves as the "air warden" in many/most cases. In addition to the basic flying of the aircraft, he/she is also checkin people into/out of the ROZ, handing out sensor assignments and updating ROZ participants with any changes to the products or plan that they received before stepping to fly. The co-pilot is also on NVGs monitoring for traffic and anything being shot at us. (trying to keep MQ-1's/9's from hitting us is harder than keeping the small arms fire from hitting us).
Before anyone says that they shouldn't be so busy for both pilots or they have too much to do: if the MC-12 isn't there, then one of the single or two-seat tactical airplanes are left to do air warden and the updates & coordination have to be done by the JTAC who is embedded with the tactical ground party and should really be firing back or keeping quiet. Bottom line - the aircraft is perfectly suited for the mission, you just have to have aviators (not auto pilot watchers) flying it.
RIP to the lost ones and condolences to their families. I hate losing brothers in arms, and I hate losing them more when there's no good reason.