I can't think of anything more profitable at the moment. Although I don't know in depth the income from online casinos.
However, to create an online casino, you need a lot of investment and be willing to pay for advertising and interact in a forum like this.
I don't intend to have an online casino, I'm more interested in having an e-commerce.
One of the factors that makes me believe this is that there is already a whole audience ready to play in casinos, as they are generally people who bet out of addiction, to make money (or even when they lose, they play just to pass the time). In addition to the fact that there are costs for servers, employees, online attendants, programmers and other costs, unlike physical casinos where the costs are for installations, maintenance, energy and employees and security guards...
Do they make more profit than digital banks, CEX exchanges, etc.?
Some time ago I remember researching a bit about this. It was not about the digital world, but it's basically the same.
Basically, there are three levels of expense. The first level is let's say a normal life, where you have rent, food, bills, etc. That is let's say X amount of money.
Then you have things like drugs, alcohol, prostitution, etc. All the vices that you can "consume" in a way. These were roughly speaking an order of magnitude higher, so 10X.
And then gambling appeared. The thing with gambling is that you can spend a huge amount of money in a tiny amount of time. Gambling spending was about 2 orders of magnitude higher than normal spending, so about 100X.
If you think about it, it makes sense... you can only drink a certain amount of beers a day, which would be expensive, but has a limit. With gambling, you can go all in and lose all your money in a single day.