Checking out the statements attributed to Mr Khoury, he was a paranoid schizophrenic. He is said to have said so early during the journey. He also said that he did not need medication. This might have been his opinion and not that of his medical advisors. the standard treatment for schizophrenia is Lithium, which turns the patient into something resembling a zombie, and which many patients don't like.
Mr Khoury's behaviour on the train sounds like a serious episode of Schizophrenia, which could be very difficult for the train crew to cope with. They moved him from one car to another when he expressed paranoia about his adjacent passengers.
He asked to get off the train, then indicated that he didn't want to get off, all in the early hours of the morning. His behaviour was erratic and threatening. He could easily have attacked any other passenger during an episode of Paranoia.
Add to this that Khoury had taken methylamphetamine, which causes people without pre-existing mental illness to act erratically, he must have been extremely unstable. People taking this (illegal) drug often exhibit strength well beyond the expected. Three people were restraining him because it took three people to stop him from doing something that could have caused harm to himself or others.
It is very common for people to die at the end of such a drug induced episode, not because they were being restrained but because the combined effects of the drugs and the stress of physical activity beyond their normal capability induces heart failure. This could appear as inability to breathe because the heart wasn't operating correctly.
This was a no-win situation for all concerned.
If the coroner had been at Cootamundra station in the early morning, I think his verdict would have been different. The combination of hindsight and limited information does not promote a fair verdict.