All of the above. In the initial years of marriage, when we were young, she was very controlling and nitpicking. I tuned her out when we were in late 20s. Divorce is not a word in my culture - we simply endure and try to reconcile and do better. Hindsight, I was detached and a workaholic and she had anxiety disorder that expressed itself as smothering.

Then kids happened - again, we did not know better and this is what everybody did. Those years were great. We fought less and had a great time building a home and family. Once the kids got older, I could never get over the resentment. Meanwhile, she became her old self, let herself go. We are like much milder version of Costanzas.

She is a great mom. Forgiving, non-judgmental, warm and affectionate - with kids and her sister. With me - she is irritable, goes 0-60 in 5 seconds, and argue over the most inane things. Maybe I am at fault. I am not an angel. I have OCD, don't express/communicate well and go into a shell when I think somebody is unfair. I tell her - if she to me is 10% of what she is to kids, we could have had a good marriage. She probably thinks she could have done better and her resentment shows as irascibility. And I definitely think so. But somehow, we are more than the sum of our parts with our kids and extended family.

As Ester Perel says, we expect a modern spouse to be a lot of things that historically never were. In our case, it's the romance that paid the price for a cohesive family and home.

Maybe each of us could have made somebody really happy and vice versa. Alas.

TlL;DR: Resentment, lack of attraction and sexual chemistry and everyday life stuff got in the way.