Feminists did not mean by that men explaining "things" to woman "as if women can't understand", but men explaining on behalf of women what it's like being a woman and specifically what's good for women. Please advise new recruits of the feminist cult (in response they will tell you, "now you are mansplaning again!" you will answer by explaining again they are using it wrong, "again mansplaining", "again using it wrong", and so on - keep at it until she gets tired).

Edit (my response to a comment):

There was some truth in that term 60 years ago. I'm around 40, but I read books written by men in the 50s or 60s explaining aspects that might be accessible only to a woman. Now - the whole trouble with the anger embedded in the word "mansplaining'" is that this writing wasn't malicious, plus, a man who works on a subject pertaining to women can attain insight on women and express important ideas about women despite not being one (for decades, female specialists have been writing about men - if such insight is accessible in this direction, it's accessible in any direction). That said, in the past men may have explained facets accessible only to women without such insight - and it's fine that women wanted to speak on their own behalf in such cases, and they did, certainly in the past half-century.

The trouble with the term "mansplaining" is not that it described 60 years ago something that didn't exist - rather the problem is, as always in feminism, that it attributed malicious intent to innocent behavior, and then was wildly exaggerated and applied to more or less everything (any man describing women - even on things which are completely universal and are not accessible only to one sex or only to a specialist; like an author describing in a novel a female character going through a typical human situation. This was also dubbed "mansplaining". Any reference by a man to women from a first person perspective, or even in general).

The problem with the term is that from its very inception it was used by feminists in a completely exaggerated way, then, used to silence men (any criticism on fanaticism in feminism including responding to "men should be excluded from every aspect of life" with "this is sexism", became "men saying something about women - hence mansplaining- hence shut up" - defense against hate speech became "patronizing") - and now the very thing the word denoted 60 years ago is done by feminists to men in complete lack of self-awareness and this time in intended aggressiveness (feminists womansplaining to men that men's masculinity "hurts the men themselves" and should be rewritten by feminist women as feminist women are the ones who know "what's good for men". This was internalized by men who were battered by feminism so severely that in attempt to be accepted as human they join in and say too that masculinity is bad for men and needs rewriting according to feminist instructions, that is, according to womansplaining of men by women). And on top of this you have girls and women applying the term today the wrong way, making the battering and silencing by it even worse.