Naturally physical attraction and chemistry played a major role. However that is common with just about anyone you decide to date or have a relationship with. I believe it's the level of comfort that comes with having so many things in common, shared values & desires, and similar sense of humor that elevated things to a new level. It didn't hurt that each of our families instantly approved of us as a couple.
However I do believe age, wisdom, maturity, and life experience plays a key role in leaning how to select the (right) mate for oneself. If I had met my wife when I was age 22 it's unlikely I would have viewed her as being "the one". Some of us need a few storms in our lives to appreciate the sun.
I've often said: "The majority of us fail our way to success when it comes to relationships". If we didn't I suppose most of us would be married to our Jr. high school sweethearts! :-)