That’s the whole point of mansplaining. It’s not about “a male is explaining something”, is about explaining something obvious that everyone already knows, almost as if talking to a child, when talking to woman. Underestimating their intelligence. It’s extremely annoying.
Yes, I’ve seen that word used the wrong way, like @Lolli42 just did. There’s always people who are too radical and ruin the original meaning and intention of the word, or just straight trolls.