Elon Musk is genuinely stupid enough to think his money would carry over after an apocalypse, isn’t he? He probably thinks that when he dies, he’ll wake up finding the whole world was a simulation but the money is still somehow valid.
Welcome to the apocalypse. We take Bitcoin.
Because civilization may have collapsed but we all still have networked computers running the blockchain 
PSA: if you see a cybertruck stuck at a light you can do a little dance with a hearty wanking motion followed by a Nazi salute, and the occupants of that vehicle will maybe run that light to escape you - at least in my neighborhood, as demonstrated by two teenage heroes at a bus stop
It’s a classic supervillain thing is to have a game in your office so that you can use it as a metaphor to talk about your evil plans. Chess, go, poker. But Musk knows those games are stupid because they’re so simple that there’s no way to win except by being better than the other player. Diablo matches his style much better because you can pay someone else to level up your character and then pretend their achievements are your own.