The reason that the Church will grant a decree of nullity = a decree that “nothing happened” is another way of saying that God did not join the two together.
The essence of marriage is a covenant (as opposed to a contract). In a covenant, both parties must intend to form a covenant relationship; when the Church grants a decree of nullity, they have found that for whatever reason (there are a number of reasons, one (or both) of the parties did not enter into a covenant.
While you have a worthy feeling, the Church has the authority (and when asked, the duty) to determine if a sacrament (marriage) occurred. If, for example, one of the parties entered the marriage ceremony with the firm conviction that if it “didn’t work out (as an example of that, if they ever felt they did not love the other individual)” then the Church would likely find that no sacrament occurred. Which is a shorthand way of saying one of the parties did not come into the marriage accepting that it was a life long commitment, and God was not joining them for life.
Many people have a somewhat limited understanding of what is necessary for a covenant relationship, and many people have very strong feelings that divorce is always, or almost always wrong. That, however, is not how the Church views the sacrament of marriage.