Alright, sometimes we might say a person's decision is right or wrong even without knowing the whole story, just like what OP is sharing. Some might say it was the right call, while others firmly disagree. If we were on the employee's side, we would take responsibility for our workers; we know how to appreciate them and when it's time to let someone go. It's not that easy to decide to fire someone over a simple issue but what I really think that happened could be more complicated than it seems, leading to firing him. Well, the court has made its decision, which means this is the final. So, even though it hurts, we must accept it.
The issue could've been getting around for some time period, and the employee might be noted for his activities. As stated, the firing isn't an immediate one. It looks like they've taken the necessary time and fired him at the right time. At some particular time of the day he might be gambling regularly. This seems to be the reason behind the firing. The authority could've gotten solid evidence and gone further if the employee raised a complaint. Anyhow, the firing of the employee is not because he used cryptocurrency for gambling. He gambled during the working hours, which is the right one.