If a gambling site's security is weak, it can be easily hacked, resulting in the loss of users' money. That's why it is important to choose a gambling site that has a high volume of gamblers patronizing them. With a significant amount of money at stake, these sites are motivated to prioritize strong security measures to safeguard funds, as well as the information and documents entrusted to them through KYC processes as one mistake could result to ruining their reputation which is a big loss for the business.
There is also one other possible way except hacking, it is by internal naughty staff of the casino who want to make extra money by doing illegal document selling.
No matter how great the security of the casino or any other online services such as exchange, we as users should realize that once we submit our personal data, then we should also ready for any risk.
There are even some official website of a government in a country which is hacked or stolen by internal staff of the government who want to sell the data to other parties.
It's definitely true that once we submit our details and documents to a website, we should know that our data can be breached at any time by any mean, whether it's done by hackers, by internal employees, by the company itself, or any other way. We should only entrust our details to the most reputable platforms hoping that they will take good care of our personal documents and they might have good security for it.
When we submit our documents to a new platform, we expose ourselves to greater risks as even the platform itself can use them in a negative way, they might sell them for money or share them with a third-party service and charge them commission for the data, anything is possible.