Mine ended because I had always been previously very independent. I was the bread winner and I did everything in the house. That suited us both fine.
Up until DS was born in the most awful circumstances which resulted in us both in intensive care and a 2 month stay in hospital for both of us followed by a year of not being able to work due to ongoing operations for me and the baby.
Suddenly, I was dependent on my DH - and he was hopeless and let us both down in numerous ways.
In an attempt to provide for us, he eventually took a job 3 hours away from home and only came home at weekends.
I coped, but began to make a life without him.
Finally, when I was better and DS was bigger and stronger and had had his final operation (a cochlear implant - he is profoundly
Deaf) I retrained, I became strong and independent again and realised I didn't need someone as a partner who could fail so completely to support me when things were tough.
It changed the dynamic. Being the strong, independent one is all good - up until it's the weaker, less capable partner who has to take over.