In my opinion the #1 cause for breakups and divorce is and always has been selecting the wrong mate for oneself.
This can happen for a variety reasons including not knowing who you are and what traits you want or need in a mate before you select one. That's the equivalent of going shopping without a list!
Most likely this type of person allows "happenstance" and "impulsive connections" to dictate their relationship choices. They commit to someone during the "infatuation phase" of a relationship before getting to (know) them. It takes time see if you're a good fit.
Some people also get married for the "wrong reasons". They had a "age goal", all of their friends were married, an ultimatum was given, an unplanned pregnancy, simply grew tired of being single or having the title girlfriend/boyfriend, pressure from parents, or one of them is going off on military duty and wanted someone waiting for them. A marriage based around circumstances is likely to fail.
The goal is to find someone who shares your same values, wants the same things for the marriage that you do, naturally agrees with you on how to obtain those things, and last but not least there is a mutual depth of love and desire for one another.
In order for her/him to be "the one" they would have to see you as being "the one". At the very least a soul-mate is someone who actually (wants) to be with you and vice versa!
Lastly women have better career opportunities and more financial independence than in many previous eras. This is to be applauded. In past generations unhappy couples often stayed together because they needed their mate financially. Divorce would significantly lower both their living standards. A recent study in the U.S. revealed 66% or 2/3rds of all divorce filings in the U.S. are initiated by (women). The more options one has the less crap they're going to put up with! LOL!
At it's core a divorce is a public admission that a mistake was made in the selection process. He/she was NOT "the one".
We're either growing together or growing apart.