Some marriages that are working today, because either or both partners doesn't have money and that's why when money comes, that's the time you see the true nature of most marriage partners. So if a couple after winning a jackpot decides to go their separate ways, it simply means that the marriage wasn't built on genuine love rather either of them was trying to be surviving on each other or both parties needed the company of each other to survive which is why they decided to split since they now know that they can survive without the help if each other with the money they got from the jackpot. Legal officers are always happy to get involved in such cases because since a huge sum of money is involved, they'll also walk away with a reasonable amount of money at the end of the whole legal proceedings.
That might not apply to most couples but yes, some couples are married but they would have clashes and fights and might even get separated if one of them manages to get rich all of a sudden either by winning a lottery or by any means. Such couples are never in love with each other but are living with each other and dragging the relationship as a compromise, and as soon as one of them finds an opportunity they can use, they won't leave it.
However, you will also find couples that would never do such a thing. If one of them manages to get a significant amount of money, they would think of doing everything for both of them because they don't want to get separate but to have a better life together. If someone is with you in your hardships, they deserve all the luxuries once you are capable of providing them that.
I really think that the number of couples that would split over an event like this is way higher than what we may believe, it is just that it is very odd for those opportunities to present themselves that could allow a couple to get such level of wealth so suddenly, however in this particular case I feel sorry for the boyfriend since it is really unlikely he will get a dime out of this, even if it was his idea to buy those lottery tickets to begin with.