I'm a longtime pilot but not an airline pilot or rated in any jets.
Armchair quarterbacking is rarely constructive as it's merely speculating. In fact, various aviation associations have cautioned members to be careful what you say if you witness an accident and end up questioned by reporter. "I saw him in the landing pattern, then lost control and dove into the ground, I think they stalled!" is a guess and not treating the pilot or anyone else with respect.
I can just give some random thoughts though. Like thinking of a couple other airline disasters such as the Atlas air flight in Houston where a 767 plunged from the sky after the pilot flying accidently engaged a go around control, panicked, froze at the controls and put the plane into an unrecoverable dive.
https://en.wikipedia.org/wiki/Atlas_Air_Flight_3591
As a flight instructor, one great concern I have is about a student locking up on the controls. It doesn't happen often, but does happen on very rare occasion without warning and there is little to nothing an instructor can do to take control if it happens, so it usually ends up deadly. Adrenalin and elbows locking is not something the other person in the cockpit can overcome with physical force. I read someplace if you put your hands over someone's eyes, instinct will cause them to reach up and try to get them off, but I don't know if that actually works, or if I will even remember that if I am ever in that situation!
Hopefully the flight data recorders will be salvageable, and if so, control inputs and cockpit communications would show, or rule out if something like happened on that Atlas air crash happened.
The other crash that comes to mind is this one-
https://en.wikipedia.org/wiki/Germanwings_Flight_9525
Again, if flight data recorders survived it can be determined if suicide is what happened.
Only other thing I can add, is that although I haven't flown with any Chinese students, there is an airport in northwest Indiana where there is a school that trains Chinese flight students, and the stories I've heard about the quality of those students are not reassuring.
It will be interesting to hear what the cause is when the investigation is finished.