the planes I fly can be held in a full stall and fly quite decently, coming down at around 1000 fpm.
That's because you still have a forward airspeed. My TB20 glides down at about -1000fpm.
If one killed their airspeed completely, that's different. It won't be easy because any certified single engine plane,
loaded within the envelope, will go nose-down and recover.
But if you were to overload it heavily in the back, then it might not recover, however, and will just go straight down.
This is outside my area but multi engine planes do not have to meet the 61kt Vs and AIUI do not have to recover from a deep stall. This is one thing which came out of AF447; an A330 can just stall/spin and plummet straight down, unrecoverably.
I reckon this one came down at a huge VS.
LSM - I agree; nothing suggests they were VMC or IMC at the time of the impact. But looking at the terrain, and the fact that they are pointing just right along that ridge, I reckon they tried to come down on it.