Honestly, I cannot tell you why you chose to stay in a five year relationship with someone you were not in love with anymore than I could tell a woman being abused why she stays, or a man who's girlfriend isn't nice to him why HE stays in the relationship.
You Were in Your Comfort Zone
What I do know is that sometimes loving someone is scary. Actually when you truly do just let yourself feel that, it's always scary. It's a risk to love someone. There's a risk of getting hurt, of losing someone important to you. There's always a risk associated.
Sometimes, that risk is too great to take and SOMETIMES, you find yourself in a pattern of comfort in a relationship.
You may or may not have realized somewhere along the line that you were not in love with your ex-fiancee. For whatever reason you chose to stay, I'm going to guess that it's partially because you were "so comfortable" with him.
A comfort zone is safe, it's secure and it doesn't usually require a tremendous risk. Leaving that safety zone can be extremely frightening and difficult, but it's important to recognize it.
You Did The Right Thing
You obviously hurt your ex. That doesn't require a lot of thought to figure out. And now, though you feel you did the best thing for yourself, you are feeling guilty because of the pain you caused him. However, consider the alternatives: marrying someone you don't love or getting divorced from someone you don't love.
Everyone deserves to be loved, and they deserve a love that is completely reciprocated. Whatever your fiancee felt for you, you obviously did not feel for him.
Though I can't say you did a favor by breaking it off, in essence you did free him to begin the process of moving forward in life. What he chooses to do with that process is HIS choice. You have to let go of the guilt, because essentially all anyone can do is the best they are capable of.
This Does Not Make You A Terrible Person
What you've done, at least from what you've told us, does not make you a terrible person. There is a difference between hurting someone intentionally and hurting someone without meaning to.
If you were in this relationship because you were using your fiancee, then yes, you have some serious soul searching to do to consider how you would treat another human being that way. And watch out for yourself, because karma does bite.
However, if you were truly making the best choices along the way for yourself that you could, you did not have any intention of hurting your ex.
Move On With Your Life
If that is the case, then you will have to realize that you both have learned something from this. Allow yourself to grieve the loss (because even though you broke it off, it can still hurt) and find a way to move on with your life.
Let Go Of The Guilt
Guilt only prevents YOU from moving on. It won't help your fiancee in the slightest if you feel guilty. He is responsible for his own process, his own method of moving forward, of learning, of growing. You cannot own that. He has his own emotions to deal with, and ultimately, he will probably move on in life and learn to love again.
He has the right to be hurt, he has the right to be angry. But that does not mean that YOU have to take on those emotions. All you can do is move on in your own life. Holding on to the guilt from THIS relationship with prevent you from doing that.