I have to mention that only the aristocratic family is secretly poor - the point of the situation is that Victor's family does have money, and the families intend to exchange the Van Dort money for the Everglot social standing. Historically, this was more typically done with a nouveau riche bride and impoverished aristocratic groom, because there was concern in aristocratic families about women marrying down, and I have written an answer before on a similar situation, which I'll paste below:

The simplest way a rich American bride brought money to her aristocratic English family was to have or inherit it herself. Historically, married English women could not own property in their own right: it was automatically their husbands'. (You can read more on that in my earlier answer here.) The Married Women's Property Act of 1870 allowed women to keep financial inheritances of up to £200 and any inheritances of real estate, buildings, or other property that came along after they were married, but men still took over anything they had inherited or been given before the wedding. (More importantly for most women but unimportant for women at the level of society we're discussing, they were also allowed to keep their wages. Prior to this, women with jobs literally had no legal right to the money they'd earned.) Married women weren't full individuals under the law, with the right to all money and property they inherited or brought to the marriage, until the Married Women's Property Act of 1882. So, any American women who married Englishmen before 1882 - like most of the women who were part of this trend - were essentially transferring all of their present and future money to their new husband and the family they were forming. Even afterward, there was significant social pressure for women to let their husbands have control of their finances, on the grounds that men were to be the head of their families and that the women had not been educated to have financial literacy. And likewise, even without legal issues there was social pressure for wealthy American parents to provide necessary funds for their daughters to live the lives they were accustomed to.

Most of the women involved in these marriages have been little studied, probably because they've been seen as uninteresting society hostesses, so there isn't much detail I can give on the arrangements made by their families. Jennie Jerome (1854-1921) married Lord Randolph Churchill in 1874, and eventually gave birth to Winston Churchill; she might be the best known, and biographers have gone through the correspondence relating to her marriage to find that there was a significant amount of wrangling over the marriage settlement, specifically what would happen to the money after Jennie died and how financially independent she could be made - her parents wanted her to be as protected as possible, while Jennie wanted to be married as soon as possible, and in the end the Jeromes capitulated heavily to English tradition. Some others who do not seem to have the same level of biographical information out there: Consuelo Iznaga (1853-1909) married George Victor Drogo Montagu, the future Duke of Manchester, in 1876; Mary Stevens (1853-1919) married Sir Arthur Henry Fitzroy Paget in 1878; Elizabeth Wadsworth Post married Arthur Hugh Smith-Barry, Baron Barrymore, in 1889, a second marriage for both; Helena Zimmerman married William Angus Drogo Montagu, the next future Duke of Manchester, in 1900; Mary Goelet (1878-1937) married Henry Innes-Ker, the Duke of Roxburghe in 1903.

In the cases of Jennie, Consuelo, and Helena, at least, they were marriages based on love/attraction as well as social and economic benefit. (Ironically, George Montagu's parents were horrified by his choice of Consuelo Iznaga and didn't even come to the wedding, and when his and Consuelo's son married Helena Zimmerman, Consuelo was horrified in turn, despite the fact that the Zimmermans paid off his debts, gave the couple an income, and bought them an estate.) Consuelo Vanderbilt, however, is a different story. She was part of the later generation, born in 1877 and named for Consuelo Iznaga Montagu, her godmother - which lends credence to the idea that her physically and emotionally abusive mother was bent on turning her into another trans-Atlantic bride from birth. Raised very strictly, she was kept away from "silly boy and girl flirtations", and once she was 17 her mother decided that she would marry either Charles Spencer-Churchill, the Duke of Marlborough, or Henry Petty-Fitzmaurice, the future Marquess of Lansdowne, eventually settling on the former. Mary Stevens Paget, mentioned above, helped to bring her into the proper circles and see that she was dressed as an attractive heiress rather than a shy debutante. Her mother invited Marlborough to Newport with them and kept Consuelo apart from the young American she was already in love with and considered herself engaged to, and after a long campaign of harassment and lying, Consuelo was forced to accept the duke. It was known even at the time of their wedding in 1895 that there was no affection between the couple, and the marriage would be annulled in 1921.