Aileronreversal?
As a retired private pilot I am amazed having read pretty much all of this thread but found no reference to what is to me the most likely cause of this crash. Hundreds of single engine pilots over the years have died attempting to do a circuit to land after an EFATO. However many thousands of hours they might have, some are obviously not aware of the fact that IF YOU ATTEMPT A STEEP TURN WHEN FLYING LOW AND SLOW YOU ARE DEAD MEAT!
They assume (presumably due to lack of training) that they only need to apply opposite aileron to level the wings! This is intuitive but fatal. They do not realise that in this situation the drag caused by opposite aileron merely stalls the inside wing promoting a spin.
Google Fairchild B52 crash for a perfect example. You can see the pilot applying opposite aileron (spoilers) as the plane, at 90deg bank spins into the ground.
The key question with regard to the Yeti disaster is, did either the PF or the captain have recent training on incipient spins? Either on a simulator or an aircraft?
All of this assuming of course that there was no defect on the aircraft.