A favorite author of mine (Eckhart Tolle) said (and I'm paraphrasing) A bored ego is a dangerous one.
And, by the way, you've officially used my favorite word "resonate"!
I resonate with the description you pointed out: (your mom was) "...unhappy, bored, paralyzed with fear, and demanding." Everyone always says how very nice my mother is and no one would ever believe me if I told them the harshness of it all.
Exactly as you found in the research "...if it wasn't physical abuse then it wasn't abuse... " and I don't know about you, but it was plentiful all the way around. The mental abuse was so bad that I didn't even know that the physical abuse was "wrong" if you know what I mean. I just thought I was a bad person and focused more on "wishing" others would validate that the physical abuse was not supposed to be happening to me. Now, I know better. Wow. To think I didn't even have the knowledge that it shouldn't be happening... I was so naive and unassuming. I've always been an angry person - and have plenty of moods... a lot like Daffy Duck, actually. But, I'm beginning to like me now. The more I see about things - about the way things really were and uncovering my mother's motives has enabled me to clarify my thinking about myself and others and her...and I find myself able to care about myself more and also to let all the negative feelings go more quickly when they arise.
I understand about never thinking to ask your mom "why", though. Let me share with you something I was privileged to happen upon about 10 years ago...
My mom had come over to my house and I was single, not married, and I lived alone. She came to visit and it felt nice having her there in my home. I don't know why but I felt a bit of an intimate feeling (keep in mind I had no conscious knowledge of her issues and no reason to suspect anything at all and didn't) so I asked her ... "So, mom, tell me something that you've never told anyone before.". "I mean, tell me something that I don't know about you". She actually obliged me and seemed eager to respond after thinking for a while. And I honestly don't know her level of consciousness about actually telling me... because it was only after I started to come into my own sense of right treatment and matured enough to tell others how I wanted to be treated that I began to see another dynamic completely with her. The more "self" "centered", if you will, that I became the more violent verbally and the more challenging she became. And, that only served to help clarify things and I could eventually see more and more as time went on. Formulating that your mother is like this is not fun and kinda well... "blows your mind" ya know?
But anyway, she began to tell me a story about her being in grade school and how there was a girl that sat in front of her in class and a pencil of hers fell on the floor. My mother had picked up the pencil and put it in her desk. She said the teacher asked who took "so and so's" pencil or if anyone had seen it and if they had accidentally taken the pencil to just return it. So, no one confessed to it and my mother was content to hide that she had taken the pencil. She actually said that she "to this day" receives pleasure from thinking that no one knows that she took that pencil and she thinks of the teacher who still, to this day has no idea who took that pencil. My mother's focus seemed to be on tricking the teacher rather than actually having taken the girl's pencil. So, the girl was just a "pawn" a "chess piece" ... and a "plaything" which is how I hear a lot of people describe the objectifying experience of malignant narcissism... and the teacher was the real focus. This story just blows me away because it's the first in a whole line up of stories that only help to clarify her adult behavior.
Perhaps I'll write more later, but as to the question of "why" I understand her past to have been very painful just as mine has been. She was not physically abused per say - but the mental abuse was prominent. I've been able to identify Munchausen behavior as far back as 3 generations since I was lucky to have had a discussion with my mother's cousin about his grandmother.
These discoveries are coming to a head more and more lately... with my insistence that I am entitled to love and care same as the next person and was blessed to have met my husband ... we were just married two weeks ago. I had my wedding in my home town and it proved to be very "enlightening". That's why I found this forum.
Long post -
I'm sorry for the pain in your life and the life of those others who have been subjected to the deeply unconscious behavior of a person with MBP. Thanks for sharing.