There is nothing about the physical world that guarantees a person pays attention because something is important. A common cause of accidents is when people do not pay attention. Train crashes specifically have happened in recent years due to distracted operators. Just because this run was more important than normal does not somehow mean the operator could not have been distracted.

> He's saying that there's things other than driver error or mechanical failure that could have contributed to the crash

Right, that's speculation.

I believe the point he’s making is that the driver’s attention is more likely to wander when it’s a routine trip done many times before.

This was the first run on the new route, not a routine trip.