not good for employees who like gambling games. but if the boss finds out about the bad habit, it means the boss has a good informant or approach for his employees.
it is possible that the employee himself told the boss in small talk. but a coworker will most likely tell the boss about his employee's gambling habits.

if I were the boss, I would not immediately transfer or fire the employee. There are concerns, but as long as there are no serious cases for the company's finances, I don't think there is any reason to transfer or fire employees because of bad gambling habits. That's his business as long as it doesn't involve company finances.