Some very powerful motive must have precipitated this calm, deliberate act of suicide and murder which took some amount of time to complete.
Based on the little info we already know about him, he seemed perfectly normal, even exemplary. But "normal" people don't just go off the rails at a moments notice, and particularly at the controls of an airliner in a situation which can only be described as deliberate and pre-planned.
The authorities will eventually get to the bottom of this and I'll bet the answer won't be Politically Correct.
Yep, his motive will be found, I have no doubt about that.