Decrees of nullity, as annie said, merely state that a valid marriage never existed.
Decrees of nullity are NOT divorces.
While one must have a divorce before one seeks a decree of nullity, it does not necessarily follow that we have “so many” because there are “so many” divorces. I believe that if you do the math, there are FAR MORE divorced baptized Catholics who NEVER seek a decree of nullity, or who, when seeking, do not have GROUNDS for the decree of nullity, than there are those who do seek it and are granted it.
It is NOT an easy process. Believe me.
It isn’t a case of somebody rich, famous, or simply “connected” just “getting bored” with marriage, or seeking a trophy wife or studly new husband, and deciding to go with “catholic divorce” in order to GET something.
It IS a case of someone average, or poor, obscure, who was not capable, or whose spouse was not capable, of entering into a valid sacramental marriage. That incapacity might be due to all sorts of factors, and not all of them might be conscious or deliberate chosen evils.
But, say, if John and Mary, age 22, marry, and John winds up drinking every night, and Mary is a shopaholic with thousands in credit card debt, John and Mary are NOT, repeat NOT, going to get a decree of nullity BECAUSE John drinks and Mary spends. In fact, John and Mary might have an absolutely valid marriage. And they might not. . .but the validity does not depend on what they do DURING the marriage, it depends on what they each brought in themselves AT the marriage.
Divorce is one of the hardest, saddest things that can happen to a person.
A decree of nullity, OTOH, while it may be difficult to go through, brings with it a true healing, even for those more “at fault”, I believe, simply because it acknowledges less a “failed marriage” than a lack of capacity FOR that (or perhaps any) marriage.
Marriage is between a man, a woman, and God. So I think a decree of nullity (as opposed to a civil divorce) is God helping us to understand that, between this particular man and this particular woman, somehow, someway, there just was not a valid marriage. He was there–He ought to know, right?