The final suggestions are good, much better than "why didn't you just". The problem comes when your initial thought is actually a good idea, and your colleague could actually have saved some time. This happens a lot in the interaction between senior and junior engineers. For those situations, it's not great to be asking for an explanation on the spot, because then the explanation is just "I'm an idiot/ignorant of that tool".

What's missing, I think, is a question that is not seeking explanation, but improvement. You are not seeking justification of actions, you are identifying an opportunity. This opens up for both an answer starting with "Aha, you might think that, but actually..." and the question "Huh? What is X? How could it be used here?"

Hence, I like

> Could it be made simpler by using `sshd`?

and

> Did you try `sshd`? This seems like it might be a good fit.