If crypto wasn't involved, do you think this employee would have gotten fired?
I think anything they were doing habitually that was taking away from their time at work would have gotten them fired. Whether that is gambling, porn, video games, stocks, crypto trading, memes, nfts, etc. I doubt his boss cared much what he was doing, only that he wasn't doing his work. That makes you wonder if he were a high performing employee, what sort of nonsense would his employer put up with as far as gambling before letting him go.
When a thing turns habitual surely it'll kill time. One such thing had taken place with employee. It is not about gambling, as said whatever he had done apart from his assigned task during the work hours is going to stop his productivity as well as the progress of the firm. This is well understood by the Boss and he had fired the employee.