A Sudden Split
There are some couples who have always known then have differences on important issues, but they learned how to keep them separate before they made a commitment. Their lack of agreement was something they were unwilling to allow it to be a part of their relationship, and they often manage quite well as a team in other areas. A sudden split comes when couples might not have realized they disagreed deeply, or an incident will suddenly bring it to their attention. They might have agreed previously, but something makes one of them change their mind, and it affects their relationship and their children.
Raising children in any age has always been difficult, but the availability of social media and news has made it more so today. Couples without agreement in the important areas of their lives can find it drives them apart, and it can alienate their children. Finding out suddenly that they do not agree on a key issue can tear the family into bits and pieces, and it can make divorce a welcome part of their life.
For those who find they will never again be able to agree, learning to live together could be too much of a burden. They might find it polarizes their children, and that is not good for a healthy upbringing. Choosing to sever their relationship could help them save at least their offspring from a daily ritual of arguments, and it could strengthen the bonds they have with their kids. They might have a better chance of keeping the younger members of the family from being in the middle, so leaving could be a good option for at least one parent.
It is never easy to realize a spouse does not agree on a key issue, but some disagreements are worse than others. Being able to at least save the children is the way adults keep their obligation to the family even if they are unable to honor their wedding vows to each other.