So why did a lack of pressurization cause the crew of AA 1646 to miss twice and also steer into the direction of departing aircraft?
Is this honestly something you expect us to answer here, or are you looking for armchair speculation? Unless one of the forum posters was a crew member that day, this isn't a question we're capable of tackling.
Seeing as that you replied I guess you did feel there was something to discuss as it pertains to this incident. And if you watched the video (which I get the impression you didn't) you would see that the lessons of this incident have indeed been addressed by AA and are now incorporated in its training curriculum.
I watched the video in its entirety. What you quote me as saying is an expansion on discussion points (1) and (2) you posted.
I have no idea why you would say "stay low" in this situation because it is quite literally the antithesis of what is taught in instrument flight programs.
Lets see. You are in an aircraft that is not pressurising, so what do you do? Keep climbing? Is that what is taught in instrument flight programs? No. Stay low (meaning don't climb higher). Run the QRH.
In my experience flying Cessna aircraft, I have gone up to as high as 11,500 feet without pressurization or supplemental oxygen while remaining in full compliance with FAA regulations and my body's own limitations. From this experience, I realize that pressurization is not a necessity to sustain life at low altitudes. I would imagine there would be problems, perhaps, with air conditioning or something that relies on pressurization to function, but it would be more life threatening to remain at a low altitude and hit something than to climb and sort out the situation. I say again, as they say in real world flight programs: in an emergency, altitude is your friend, and you should climb.
An example of good CRM for a far more complex problem occurred when QF32 experienced a turbine failure that also degraded two other engines, damaged hydraulic and fuel lines, landing gear and flight controls. What did the crew do? They flew a holding pattern while they addressed ECAM actions and landed about an 1 hour 45 minutes after the turbine ruptured.
I'm not suggesting the crew would get an A+ on CRM in the original incident. I'm not sure why you followed up with this.