The biggest question is why would someone carry 10+ BTC with them if they are also going to a country known for crime? Maybe this happened because one of them posted something on social networks, and maybe they really paid something with BTC in that country and thus drew attention to themselves.
It is also possible.. where when someone shows off the money they have, they could be targeted by robbers... but there is something else that could happen in such an incident... such as when a robber forces to take the victim's cellphone, then checks what applications are on the victim's cellphone... when they find an application related to cryptocurrency, such as an exchange, telegram bot, crypto wallet or others... then the robber spontaneously realizes that the user must have a cryptocurrency balance... from there the threat will start to be used as the most effective action to seize all the victim's cryptocurrency assets....
In addition to not showing off on social media, we should also limit other people's knowledge that we have cryptocurrency... don't let our friends be the masterminds behind the robbery. Keeping our cryptocurrency a secret is probably one of the best ways for us to avoid such problems.