Although the news media and the law enforcement personnel both think they have to list all the various possibilities, as to the cause of the accident, they really should not, because all they mostly have are their personal opinions and speculations and conjecture.
Seldom do these people have concrete proof or evidence when they report on it...they have no idea if the guy was sleepy or tired or not...they certainly do not have any idea of any medical conditions since these are supposed to be private...unless they found medicine bottles at the accident site, then they still really do not know....they are not doctors either.
Now if they find evidence of liquor in the truck or on the driver, they may be able to say something definitive,,,but what if this so called evidenced was planted?
And what if mechanical failure was the cause? oftentimes these can not be detected by pre-trip inspections.
Unless all the various and sundry possibilities are listed, then it is irresponsible for any possible causes to be listed, until after the experts have concluded their investigations and analyses.
When I get my news, all I want is the facts, not a bunch of guesses...and fake news.