As far as I know, not only does the government not allow gambling, but the people of the land of kimchi also have a very negative view of gambling. So I was not surprised by this news and even thought that this was a pretty light punishment for an employee caught gambling at work. South Korea is a pretty crypto-friendly country but very strict on gambling, so this guy's firing has nothing to do with crypto but gambling.
Not to mention, banking is an extremely sensitive field because it involves people's money, what if he is addicted to gambling and steals the bank's money to gamble? In my opinion, this guy deserves to be fired.
Wish story would be more full. South Koreans are not allowed to gamble, but foreigners can gamble in South Korea. Imagine how this story would look if fired employee was hired foreigner. I would also wish to know how exactly they found out he was a gambler. If he has used bank PC for gambling, that is inacceptable. If he has used his own mobile, then banks interference in private life in inacceptable.
When I was studying in university and passed practice in bank, was nearly impossible to do anything extraordinary with bank clients money for a regular employee. Higher bank stuff more rights and access, but they doubtfully would steal anything. So I would say that for a regular employee it is zero chance to steal and use money for gambling.
Even if you are a foreigner, in addition to government regulations, you also need to comply with the regulations of the bank/company where you work. You are their employee and you need to follow their rules, and with the anti-gambling culture in Korea, it is no surprise that banks would prohibit gambling.
Whether he used the bank's computer or his phone to gamble, it was the same, since he gambled during working hours, his superiors had the right to handle it according to company regulations.
Stealing money from a bank/company is never easy but for a gambling addict with no money to gamble anything is possible.