It’s still up to them to ask. If they want to know the whole causal chain from distal to proximal, so be it. And if they never ask, I doubt it would help at all trying to explain anyway – they’d just zone out – and might be a good idea to start looking for a new job.

In any case, the actually important question "How to make sure this won’t happen again?" would presumably include the relevant parts of what "this" is as well. But in a more actionable frame.