The captain did have a couple of significant events in the days leading up to the flight with his wife and kids moving out and his political hero being sent back to prison for sodomy.
A pilot with marriage problems and strong views on politics, well blow me down.
But a pilot who murders his passengers and hides the plane where it can't be found? Is that likely?
I am not saying it is impossible, but the fact that his wife left him is not really evidence that he is to blame. I just don't think it is justified add A + B and get C like this, otherwise I am never getting in an aircraft again.
Assuming this was deliberate act, then it seems to me at just as plausible that there was a motivated yet competent lunatic amongst the passengers who worked out some way to get control of the flight deck. You don't need 18,000 hours experience to fly a plane into the sea for instance.