I don't think If there had been a more profitable business than real estate and professional services but while you compares between digital banking and the CEX, I think online or Crypto casino would take the lead because the online casino is factorized that it is not limited to restrict certain persons as regional sentiments.
Besides the online casino is not based at a physical location, so it can always be accessible for any interested persons anywhere anytime.

If the required resources such as campaigns and the media is setup for speculations of course yeah, there would be numerous gamblers willing to visit the casino sites to place their stakes at most of their conveniences.

Moreso, I support the motion that the online or Crypto casino is more profitable than others digital business in the sense that whatever fund lost by the gamblers totally belongs to the gambling company and it is agreed that gamblers looses more than they wins.

Banks Only relies on making profits through transaction fees and loans which the digital banks are limited to offer their to certain persons by restrictions and due to regional sentiments.
So obviously the online casinos do have more customers with strategies to retain their customers funds on the services of staking and loosing.

They could actually be a better digital business than the online casinos which I may not be aware of.