If crypto wasn't involved, do you think this employee would have gotten fired?
It’s same scenario. It’s conflict of interest for someone who work in the bank that has gambling habits since they are prone for addiction.
The court will not side with the bank if there’s no terms that backed the company to fire the employee. You can consider this case as high risk for the bank to have a gambler employee. Besides, how will the bank knew that he is gambling if doesn’t show any sign of gambling habits at work.
It also depends on the ability the employee has to manage money of the bank and whether they could misuse deposits of clients to gamble with them. Let us see the case for example of someone who works on a bank and yet, does not directly manages money, during that person's break time they could be gambling and there should be no problem about it, because there is no plausible risk for a person to make the company to suffer a substantial loss of money with their gambling sessions.
This that case the courts would have sided with the person getting fired and demanded the bank to economically compensate the victim.
Anyways, I am pretty much sure within the hiring contract of banks and any other big companies there are hidden paragraphs about gambling and other unacceptable activities which are not supposed to be partaken in during one's shift. One is very likely to ever win against a company/bank that has an army of good lawyers backing it up.