Yes I agree, they knew about the possibility of runaway stabiliser and they were not morons. Boeing’s guidance was useless to them because it left out a description of how MCAS operates, and I’m not sure it even mentioned it by name but I may be wrong on that.

If they had known that MCAS is disabled for 15 seconds by pilot trim inputs, they could have saved the plane. Toward the end of the flight they went off-book and re-enabled auto trim, blipped the trim a few times and 15 seconds later MCAS jumps on and dives them into the ground. All they needed to do was keep making small trims.