This can really be condensed to only three, since some are redundant if you know the underlying cause. It's not like a research study is needed if you know people with successful marriages. The factors they chose that have an impact really only reflect the relevance of the following factors:
1. Taking marriage seriously. Eloping or skipping a honeymoon says "I don't want to invest much in this." Even those with moderate income can have a modest wedding and inexpensive honeymoon instead of going all out. Any indicator of not taking the marriage seriously is a negative, no matter what form it takes.
2. Genuinely valuing the other person for who they are. Hence, this means to not be a gold-digger or care more about looks. Also, dating longer is just an indicator that "finding the right person" is the attitude the person is taking, which means they want the person as a person to be a good match. By contrast, looks and money can be identified immediately, so it doesn't require a long time to get engaged. Desperation is also not a good reason for marriage, and desperation doesn't need a long time to get engaged.
3. Having a deterrent for divorce. Rich people, church-goers, and people with lots of people at their wedding have a lot of people to pressure you to stay together because you lead *public lives*. You don't get a private divorce, you get public embarrassment. Rich people have an additional deterrent in that it's a lot of money to lose if your ex-spouse wants to take you to the cleaners.