The leading cause for divorce is and always has been selecting the wrong mate.
Most of us don't take the time to do the introspective thinking required to figure out what we truly want and need in a partner.
Once you know what you want you have to be willing to take the time to find someone who "naturally" wants what you want.
A lot of people become engaged during the "infatuation phase" of a relationship without knowing many things about each other.
Sometimes people get married too young. Mabye 30+ is an ideal age for a first marriage. (Hopefully by then a person has completed their education and began building a career).
Lastly doing things in the wrong order causes mistakes.
Ideally the following should be established in this particular order before saying, "I do".
1.Honesty, 2.Trust, 3.Loyalty, 4.Love & Devotion, 5.Intimacy, and 6.emotional security. (These steps require time)
The vast majority of my failed relationships began with step #5 and then I attempted to work my way backwards!
There may be some exceptions but for the most part it rarely works doing things that way.