No plausible reason?
Well, give it a few days and we can learn the implausible reason then.
"Airspeed is Everything," you say? So, your students tool around staring at the ASI? No, of course not so that I think you are oversimplifying things here to make this accident crew out to be really incompetent when there might be more to it than that.
Don't let this come as a total shock to your preconceptions but many professional crews make really gross errors. That is a fact but why that occurs must often be down to educated guessing.
There is an old Jewish proverb that states that a fool can ask a question that a thousand wise men couldn't answer. Large teams of highly-qualified people can develop a modern aircraft yet we still find ways to crash it, when I suppose they must sit back and ask, "How in the world did they manage to do THAT?"