I know. But I've seen it on larger transports than this one. In that case it's what happens when a) automation is relied upon and the company has bought the sales pitch, and b) when pilots yield authority to the automation and are "uncomfortable" disconnecting through lack of practise and knowledge.
Both are training matters - the first a philosophical one and the second a money one.
In either case, monitoring is the requirement and it is a well known fact that humans are poor monitors.
This is a comment about automation and not about this accident. It may or may not be a factor here.