The Catholic church cannot and does not prevent civil divorces. The divorced parties are entitled to all the sacraments offered by the church, as long as they have not remarried. They are still welcome to attend, but are asked not to take part in Communion, could not have any children from the new marriage baptized as Catholics. The church has ministries to help a divorced catholic.
If a person, married in the Catholic Church is divorced, that person can seek an annulment. It is not an easy process, but it is certainly doable. If both parties agree, it goes petty fast. Infidelity would be one reason to grant an annulment, the fact that the couple had not made a real commitment to the marriage would be another. You must have the civil divorce before coming seeking the Catholic annulment.
There are a lot more details and other reasons why annulments may be granted. Perhaps some have been denied, but I do not personally know of any.
I had a friend, who sought a divorce from her husband. It was granted. She has no intentions of ever remarrying, so she is still a Catholic and entitled to all the sacraments offered by the church, as is her former husband, as long as they do not get married again.
The marriage ceremony in the Catholic Church has the line that goes something like, "What God has joined, men must not divide." In the Catholic church, like most churches, marriage is expected to be a lifetime commitment. That is not always the case. Each Christian faith has its own way of handling it. Catholics do get divorces. Some get annulments and remarry and stay in the church. Some leave the church. They will always be welcomed back.