OP was just giving his guess, OP never asked him directly why he did that, so we really don't know what his intentions were. In this case, OP should talk to his friend who invested in bitcoin and should explain to him the risks of disclosing his bitcoin to others. If he is a braggart, he deserves to be criticized and condemned, but if he just wants to convince the other friend, OP should explain to avoid making the same mistake again.
I believe that we should be considering the situation as something related to ignorance, because ignorance isn't really a thing about everything, a person could be wise and smart about one thing but ignorant about a completely different thing. This person could be ignorant about this subject, and that is why it could be the reason why he may do something risky and endangers people around him, not with intend, but more about not knowing.