The pilot chose to climb to 38,000 feet, only 1,000 feet shy of the A320-200's service ceiling, in a plane basically fully loaded. That means the ceiling is actually lower and this would be illustrated on charts the pilot has in the cockpit which he is trained to refer to. The flight envelope 1,000 feet below the plane's ceiling will be very thin, even thinner when loaded - assuming it can even reach that altitude with that load - and to top it off he's headed toward a thunderhead which is illustrated by the lightning map which has come out since the crash. The plane probably failed to get above the rapidly rising thunderhead. It flew through it, the updraft pushing the plane above its service ceiling, the autopilot failing to maintain control and disengaging, the pilots unable to maintain control because the plane can't maintain flight at that altitude, the plane stalling, the pilots failing to recover from the stall because of faulty instrumentation due to icing encountered in the thunderhead, the engines flaming out, basically everything going wrong, and the airline eventually being driven into the ground by pilots who failed to get the engines restarted or recover from the stall properly.
I think my theory is pretty realistic. All of the things I mentioned have happened before and there's no reason to believe they can't happen again.
