There is zero question that this was deliberate, as opposed to health-related. Airliners are not hand-flown at cruising altitude. This aircraft would have certainly been under the control of the autopilot/FMS at this point, and had the copilot been rendered unconscious for some reason it merely would have flown on in level flight until it ran out of fuel.
I agree- no question. If not an “act of terror”, this guy was on a suicide mission.
This is just so unbelievably horrible. Those poor passengers had to be terrified, once they realized what was happening.