Explaining triggers a status check before it triggers understanding. When you correct someone's facts or logic, their brain registers a demotion first and the content second. That is not a character flaw in them, it is how status works between people. You can be completely right and still lose the room because you led with the correction instead of the person.
Part of the mechanism is the word 'why.' Asking someone 'why did you set it up that way' sounds like an audit. It puts them on the stand and their first move is to defend the decision, not examine it. Once someone is defending, they stop thinking and start justifying, which is the opposite of what you want if your goal is to actually fix the thing.
Swap 'why' for 'how.' 'How does that piece handle the edge case' or 'how would that hold up if volume doubled' asks them to think forward instead of defend backward. It keeps them in problem-solving mode, which is where you actually want them, and it gets you the same information without the status hit.
The other lever is sequencing. If you explain before you've shown you understand their version, it reads as grading. Understand first, out loud, then explain. That ordering alone removes most of the defensiveness, because now your explanation looks like a continuation of their thinking instead of a takedown of it.
"Why" questions ask someone to defend a decision; "how" questions ask them to think it through. Same information, no status hit.