Of course, marriages are intended to be lifelong. But in this imperfect world divorce can sometimes be lifesaving. (Even God has been through a divorce. That's right, click on the above link, "Is Divorce A Sin?") The widely used verse in Malachi, where God seems to state that He "hates divorce", is mistranslated. What God hates is literally "the putting out" of a woman.
Putting out is altogether different than divorce in Jewish culture. A man would permanently kick his wife out,denying her the Jewish divorce certificate. This woman would still be legally married, but with no home. Her dowry and children would be retained by the husband. She would have already surrendered her virginity to him. She would be ineligible to remarry, since technically, she was still legally bound to her husband. Further, her culture would label her as an adulteress since she did not have a valid divorce certificate. And this lady couldn't just rent an apartment and get a job teaching kindergarten - there was no place for a put out woman in Jewish culture of that day except prostitution. Since the marriages were most often arranged, this whole horrible chain of events would have been completely out of her control.
The husband, however, was free to marry again and to do this as much as he liked. That is why Moses required a divorce certificate to be given... so that the marriage was legally, fairly, and religiously terminated and the woman would be free to remarry and go on with life.
For more info about this topic, do a search on the word "agunah". That means "chained women". The act of putting a woman out is still happening and today there are 1000s of "chained women" in Israel! A Jewish divorce certificate is so valuable that often after a man puts out a woman, he will legally obtain the certificate and then sell it to the highest bidder. "Agunah" is one of the greatest problems faced by orthodox Judaism today.
All over the Bible we have ignorantly and clumsily translated "put out" as "divorce". This has caused many errant doctrines to be formed and made a terrible mess out of millions of people's lives. The toll in human suffering because of our ignorance is overwhelming. The Bible simply does not say that God hates divorce. It says that God hates the putting away.
In the New Testament, Jesus continues to address this cruel breach of human rights. Nearly all of the verses translated "divorce" in the Gospels actually say "put away". It is a completely different situation which we have no equivalent for. Knowing this makes a world of difference. For instance, many believe that Christian remarriage is adultery. But Jesus did not say that if a man marries a divorced woman, he would be committing adultery. He said that if a man married a "put out" woman, he would be committing adultery. This is because she was technically still married! In Israel, putting a woman out is a devastating, intentional ruination of a woman's life. God still hates it.
We have mangled the meaning of what is going on here and used it to place people under a different type of legalism. The worst result of this mistake is that when a marriage does break down, people will often believe that God rejects them, and they will lose their faith just when they need it the most.
There are myriads of reasons why marriage relationships break down. God hates it when a heavy, inflexible grid of legalism is imposed on people and they are broken and turn away from Him as a result. It is obvious that marriages are intended to be lifelong and that every attempt should be made to reconcile and to recapture the first love that founded the relationship. But in this imperfect world, God's provision of divorce is sometimes vital, and can be lifesaving.