1. Man is reasonably old.
2. Man is wealthy.
3. Girl is super young.
4. Girl is pretty.

The wealth of the old man and the beauty of the young wife will help nurture the best offsprings..

Plus, a young wife has smaller baggage compared to older ones. She's impressionable.

She's malleable.

The huge age difference and wealth makes it easy for the wife to be submissive. Also, the presence of wealth allows the wife to be more feminine.

The wife is not bitter because of unfulfilled old age. ZERO feminism.

She knows that her juvenile opinions do not matter to a successful and experienced man.

Even more important:

The marriage allows both parties to cheat without stress.

Reason:

1. Husband is a successful man that's likely to be EXTREMELY busy which usually involves traveling. On these occasions, he can cheat to his satisfaction.

2. Because of husband's busyness, the young wife also has ample opportunity to Bleep men her age.

3. Even if the husband is caught cheating, the wife is not threatened because there's enough money to go around. Plus, a very expensive apology is sure to follow.

4. Wife is unlikely to be caught cheating. Her extreme discretion is guaranteed. Plus, a wealthy man is often secure and cannot countenance any woman will cheat on him.

Overall, it's a jolly arrangement.

The scenario you painted is not the case in most marriages we see today. These are exceptions