This isn't so much a bet on bitcoin as it is a bet on virtual currency. If another currency trumps bitcoin, Coinbase will become the wallet for that. So as a VC, if you buy the digital currency story, this seems like an intuitive investment.
How do you think bitcoin works? Instead of the central bank deciding, an algorithm does.
You're prefectly right. Last time I sued HSBC for money laundering and Goldman Sachs for maket manipulation I got a ton of cash and they learnt their lesson. Bringing the FED down to its knees was even easier.