I would say, from my own experience with my first husband, that it happens bit by bit. And then you have a small child in the picture, and you don’t fight the inequality because you are busy and you don’t want to ‘create a nasty atmosphere ‘ in the home. And you are tired from your job and your commute and from the dinner, bathtime, bed routines, and you don’t want to fight about the inequality, so your pour a glass of wine, take a deep breath, and just tackle whatever the evening brings. And then you are so embarrassed that you, the smart graduate, good at your job, competent and energetic on so many fronts, have been so comprehensively bamboozled by a selfish shit who cares not a jot for you, and that this is your life, that you resolve to just plough on and do it all. Until the day you absolutely cannot put up with it and you leave.
I had checked out mentally, sexually, emotionally, and i guess the next step, after 8 years of this worsening life, would have been to divorce. But THANK GOD, the lazy, selfish sot got cancer and died quite quickly, leaving me, it is true, with a mortgage, a small child and not much money because of course no life insurance or pension provision; but I was free and I hadn’t had to fight for it. (He once told me he would burn our house down rather than split it in a divorce.)
So at least some of us, OP, make terrible choices and then shame and pride stops us from acknowledging that fact. We soldier on. If this rings a bell with anyone, i wish you strength to leave.