It is perhaps a proof of ability, burning a zero day might be worth it, if you have others you can sell, also if the zero day was one time use or likely getting closed soon , the value might be not as high as it may look.
I've been thinking about this for a bit. Perhaps these were crypto scammers that discovered a God mode and used it. To actually monetize this hack in another way would mean getting in touch with some truly powerful/evil people and possibly putting yourself in danger.
Creating a couple of wallets and a website can be done mostly anonymously. Sure, the money is a lot less, but so is the risk.