It's better to tell the actual situation to know if he needs more emotional help. They tend to hide it but the real thing is that they need help from someone but they are shy to tell it because they will be judged as they thought.
I agree, but the way to never force him to tell his gambling defeat, we can divert the conversation as if we have also experienced a high loss and are willing to accept someone's motivation not to repeat the same thing in the future, so that way is more effective to make he is open to talk about the details of his losses.
It will depend on your technique on how good you are as a conversationalist, you can convey topics that you can base on how you talk but not everyone can do it because not all of us can divert the topic into telling others their real struggle, especially in gambling.
There is the type of people that won't be open in telling their struggles so does the impact of the market not just on their own portfolios like bitcoin and as well as gambling.