Not sure if it will help, but quick marriages are really characteristic when one partner is abusive. They start with a phase of "love-bombing", where the abusive person idealises a new partner, starts copying all their interests and mannerisms, making big promises etc so that the impression that they are "soul mates" is created, and the relationship is fast-forwarded into marriage, home-ownership etc before the couple has truly got to know each other.
However if the abusive person has not done not done any work on themselves (by which I mean a sustained period of therapy or self-reflection and journalling, understanding themselves and their contributions to previous relationship failures) then they will not have actually changed. They've just impulsively thrown themselves into a new relationship that looks great from the outside but is likely to be a very different story on the inside before too long.
If your ex really is narcissistic, her life will generally look great to the casual/distant observer because narcissists are highly invested in having everyone believe their lives are perfect. Of course, this impression is only created because the narcissist shamelessly lies about how they really behave and engages in impression-management to make everyone believe their lives are just fine.
Everyone sees the happy Snapchat shots of the big day, but if there's a nasty fight in the hotel room after the wedding when your ex tears strips off her new bride because she "drank too much and embarrassed her" and she "can't believe after all the money she spent on the wedding her wife is begging off sex because she's apparently too tired" then you won't see that on Snapchat, will you?
Often narcissists partners go along with the "everything's fine" act, because even though they're being treated badly, they are telling themselves that the narcissist only treats them badly because they somehow deserved it (even though the faults that the narcissist is telling them they have are usually completely made up - more shameless lies), or that the narcissist has had a very hard life and their behaviour 'isn't really their fault' so they're trying to protect them from the harsh judgement they would get if people really knew what they were really like.
It's only when you have been on the inside of a relationship with them that you know that the "happy families" impression is all smoke and mirrors, and not a genuinely great relationship.
Honestly, go to therapy. It will help you sort your head out. You are still stuck in believing that the way she treated you was due to some fault or failing on your part. It's not - I can say that without knowing one thing about you. It may be hard to get your head around, but the way others treat you isn't about you, it's about THEM. A decent person will always treat other people with decency, or disengage with them decently. If your ex didn't treat you with basic respect, then that's about her lack of decency, not your lack of worth. Your part is to learn to see when someone is not treating you with basic respect and refuse to accept it.
You say you put yourself through all that for nothing, but it doesn't have to be for nothing. It can be a trigger for you to learn to see and fix the mistaken ideas you currently have about what a good and healthy relationship is, and learn your own self-worth.