Ran out of airspeed?
Only the black box info will contain the data to refute my theory but after reading everything I can find, and if I were a betting man, my money would be on:
After flying three orbits to establish a degree of familiarity with the weather and the layout the crew prepared for a single visual approach remaining VFR below the clouds and ready to climb out for a divert if they weren't happy with the situation.
They set up an approach configuration similar to one they would have employed on a glideslope and flew under the clouds towards the runway, with at best a marginal approach speed for the conditions. With the pressure of keeping tabs on the aircraft orientation and looking out for landmarks and the looming runway lights, suitably increasing engine thrust after they levelled out could well have been missed. As they approached the runway and encountered rising ground, and increasing thrust to compensate, the high drag configuration might have prevented an immediate climb-out, and the aircraft sustained enough damage after hitting a tree or trees making any further recovery impossible.