Can I conclude that reasonably non-forecastable event(s) occurred fairly late in the flight?
You won't get flamed for asking logical and sensible questions, especially as you admit to not being a pilot.
Your analysis would appear to be a good guess and your final question is what we would all like to find out!
Unfortunately on every occasion where an event like this comes to wider attention everybody has an opinion on what they did wrong and what they should have done before the full story is known.
Naturally this will always anger those of us who operate aircraft for a living and don't engage in what our American cousins so aptly call 'armchair quarter - backing'.
It is especially galling to anybody working for a decent airline where safety is probably without exception at the top of that airline's agenda.