I’m unmarried, but for what it’s worth…
I think some people get divorced because it’s the only way out of a toxic situation. An abusive spouse, a spouse preventing them from practicing their religion, a chronically cheating spouse, a spouse unable to control their anger, alcohol use, or drug abuse in front of the children - all of those could be reasons for a Catholic to choose to divorce their spouse.
Some people get divorced because they have no choice - their spouse makes that decision for them, and try as one might, they can’t force another person to stay in a marriage. Some people are abandoned. Some people are cheated on and left brokenhearted by the cheating partner.
Some people divorce because they can’t handle the pressures of marriage. They don’t learn to deal with a spouse and children, they’re stressed out by the demands placed on them, they can’t manage their own life and that of their family. Sometimes it’s because their spouse is away too much, or not giving them the emotional support they need. Sometimes it’s because they didn’t realize that marriage wasn’t their real vocation. Sometimes it’s because they have health issues that interfere with their ability to manage family life.
Some people divorce because they’re immature or selfish. They run into problems and they’re not interested enough or committed enough or mature enough to try to work through them. They’ve been led to believe that marriage is all about the happily ever after, and they think that they’ve made a mistake and God must have some other better person out there for them that wouldn’t disagree with them the way their current spouse does.
Some people divorce for good reasons. Some people divorce for bad reasons. I don’t think many people enter marriage imagining that divorce could happen to them, but nonetheless, sometimes it does. I don’t know if there’s anything that can be done about it. Prayer, discernment, and marriage preparation are good ways to protect yourself against divorce, but still there’s no way to be sure. We can’t always be sure what God’s plans for us include.