I've been an ALPA member in good standing for 8 years.
I think it's a slap in the face for every pilot that operates to the highest standard possible, when ALPA defends complete unadulterated negligence.
Not once does ALPA National or the 9E MEC mention the probable cause of this accident!!!:angryfire They only focus on contributing factors!
So you say in your post that you wanted the most probable cause of this accident! Here it is;
This jet crashed and both crew members died because they were goofing off, playing around when they should have been flying! I bet the Captain was trying to impress this F/O and took him up to FL400+ There is another example of this behavior at Express/Pinnacle- around 10 to 15 years ago a Saab 340 Captain and his crew were flying alone one night. The Captain asked the F/O if he wanted to shut an engine down in flight. They did! When it was time to restart the engine the Captain told the F/O go to row one with your flashlight and watch the prop come up to speed(bland angle change) The Capt then started to engine with the power levers in ground idle instead of flight idle. The airplane spun out of control and lost thousands and thousands of feet.
It's sad to say, but truth is these guys poor procedures, poor airmanship, inmaturity, and poor training caused this accident plane and simple!