There is a motive for a State 'hacking down' (as opposed to shooting down) a passenger jet and it's the same rationale that would be used to shoot one down. And we know Governments WOULD shoot down a hijacked plane as a last resort.
It's not communicating.
It's flying erratically.
It looks like its been hijacked or is otherwise (fire/hull breach/hypoxia/suicidal pilot etc a threat to cities or other important targets.
What if you took the dreadful decision to hack down an incommunicado AWOL jet you thought had been hijacked - but it hasn't actually been hijacked? There was some other explanation for pulling the comms and flying weirdly?
In any case you daren't let the world know you have the technology to cyber jack and redirect a hijacked plane.
Fuck knows what's been going on but tbh I doubt we will ever know.