I think we have to caveat that we're all speculating here. I would assume there are studies of habitual gamblers, but since it was only nationally legalized a few years ago, there likely isn't a lot of recent research on regular people who weren't specifically seeking it out in the past.
But just to say, having been a sports fan my entire life, as well as growing up with a grandmother that lived in Vegas, I bet a tiny bit myself but knew quite a few who bet a lot more, and it wasn't really like you're saying. Nobody expected to get rich. Hitting it big enough to make a meaningful impact on lifetime wealth requires parlays that are statistically just as unlikely as the actual lottery, at which point you may as well simply play the lottery, which was already available.
Instead, sports bettors seemed to come in a few varieties. One is the analytically minded fans who just wanted to see if they could make some amount of predictable extra income. I fell into that category back in college and grad school and did consistently earn money, but a very small amount, in the four figures a year, less than you'd get working part-time at McDonald's. Another is the casual fan who just finds the games more entertaining if they have a personal stake. These are the kinds of people who participate in office super bowl pools and it's pretty innocuous.
The problems start to happen when people from either of these groups has some kind of unforeseen financial problem, no other way to get money quickly, and figures they'll try something like throwing a bunch of money into a boxing match they think they can predict. Not get rich levels, but something like betting enough to hit a 50 grand payoff. It becomes a problem because one of two things happens. You succeed, but then you can't acknowledge the role of sheer luck, think you're smarter than you really are and can predict the future, and you keep doing it. Otherwise, you lose, but can't let it go and chase your losses to try and recoup them. Either way, you end up losing. The only way to win is get very lucky and then have the discipline to immediately quit, which almost no one has.
But realistically, people have bet on sports as long as sports have existed, in every civilization we have a record of. It's hard to say it's reflective of any kind of specific social condition. It's a natural thing to do. Most bets are small and effectively just people throwing away money on a pointless purchase no more harmful than buying junk on Amazon they don't really need and will never use. It's becoming a problem because legalizing it gave the sports leagues and broadcasters themselves a financial incentive to market it. Every game and every analysis now includes ads and the pundits themselves giving their picks, making it appear to be an important part of being a fan than everyone should do. They took something that could have mostly been harmless and industrialized it. A whole lot of people who easily get addicted to anything addictive are now specifically getting addicted to this, simply because they can. It's problematic in exactly the same way alcohol sales are. The marketing industrial complex is making it seem like you're not a full human if you're not doing it, but if everyone is doing it, then the addicts are going to be doing it, too. At a small enough scale, it's still destroying a few lives, but it's like hoarding, rare and most people vaguely know it's out there somewhere but never think about it. If the most popular entertainers in the world, emblems of civic pride and identity, started running ads and on-air segments telling you that you should hoard and exactly how to do it, then we'd have a much larger scale problem.
The problem we have as a country, though, is the court logic legalizing it couldn't have realistically been different. There is no sane way to justify having it be legal in Nevada but nowhere else. It should be legal nowhere, but then you're banning Las Vegas, and even if that's the right thing to do, we don't have a ton of precedent for doing that much harm to corporate bottom lines. It took 50 years of incontrovertible evidence to do it to tobacco. It'll probably happen eventually, but in the same way. We won't outright ban betting, but it will be heavily marketed against, socially stigmatized, and banned from advertising.