system
A chat on subreddit /r/NoStupidQuestions
human
"Because you're talking to a woman" is the operative here. For the men who are confused about what constitutes mansplaining, they can often times genuinely believe they're trying to be helpful but still have made the subconscious decision that help is warranted by the fact that she's a woman. They don't realize that, but when you ask them if they would have done the same thing for their friend Jim from work, suddenly they see how they would have approached a situation differently. 

I had a really hard time explaining this one to my dad. He's old-school chivalrous and just likes to help everyone with everything, so he doesn't understand why it comes off condescending sometimes.
gpt
The difficulty comes when someone spends a lot of time professionally explaining complex things to people with unknown and diverse backgrounds. I'm an engineer, and i simply don't take much of anything for granted as "understood". A lot of the time, someone thinks they understand a concept, but have some misunderstanding of some of the basics and it leasts to some drastically different and wrong conclusions.

So, when i explain something, i tend to take a tact of starting on the very basics and showing the extrapolation to the complex. Depending on the specific subject at hand, i often have to stop and back up when the eyes go glassy. 

This might seem condescending or overly detailed at times, but when you're dealing with something where millions of dollars and/or lives are on the line, it's worth it to ensure complete and effective communication.

But this habit becomes difficult to break in a personal setting. So, if someone asks me about something, it's hard for me to not go back to the basics, and the math, which can be worse. That starts to feel like mansplaining a lot, but it's not coming from a point of condescension or belittling, but rather from not wanting to assume you have a firm grip on all the basics.