If it is wrong for the owner to give the loan then the borrower is more guilty. Since the owner operates a casino or gambling business, he can certainly provide loans to grow his business. On the other hand, the person taking the loan should also be aware of whether he can repay the loan amount or not. When providing loans, sometimes such situations have to be accepted. It would have been better if the financial condition of the borrower could have been well known before giving the loan, then it would have been possible to prevent such a situation.
Both of them have fair shares of wrong in this scenario. The owner shouldn't have provided a loan in the first place if there's really no existing feature of such in his casino. Additionally, someone shouldn't be granted with one without knowing the financial capacity to pay of the borrower. In this case, he was not on his guard and do not expect bad things from happening. You can say that he trusted the gambler to pay, however, it became a trouble to him.
Meanwhile, the gambler has his wrongs too. He shouldn't have borrowed if he knew he can't pay. It is the debtor's responsibility to pay his dues, and he must know that already to avoid inconveniencing others and himself as well because of the additional interest generated from the debt as time passes by. But he insisted to take a loan and didn't bothered to pay at all. It's such a shame that there are people who are like this.
Hopefully, there will be no cases such as this in the future and the players and casino owners will learn from here already. Because money matters should be taken seriously and responsibly.