Sexless marriage and divorce
It is still our free will to make our own decisions. But I believe there are signs & feelings that try and influence us or not. My case was I married my first wife, we were close for 7 years, had 2 sons, she cheated on me, wanted to be single again & 20 years later, she still is & bitter.
I married my 2nd wife, we were happy, but had a lot of conflict with "our" daughter, that caused marital turmoil, with me being #3 on the totem pole. There is now a grand daughter, so I'm mostly #4. Our marriage is more of a companionship that I've learned to live with. I fought hard for the past 3 years to re ignite us but finally gave up.
Once they "fall out of love", for whatever reason, you rarely get them back. A true marriage isn't rocket science. You love each other, you want to be happy, you do what you have to willingly & you stay close. It always takes two.