Because I Am Bored
If you strip the envelope of crypto-hate, this is a really interesting idea to put transaction-validators on space-probes that are rapidly moving away from Earth.There, they can't be coerced by terrestrial bullies - be they 'authorities' or criminals – or enlisted into new cartels. They'll be running the same audited code for as long as they're in operation, unless later probes can outrace them.And if the economic effort that had been spent trying to corrupt terrestrial nodes is instead directed to ever-more-cost-efficient planet-leaving tech - that's a win, too!(Maybe ʻOumuamua was the leading edge of some other solar system's cryptominer cone?)