That's overly simplified: Google's stock value is based on a history of successfully competing in advertising and receiving billions of dollars, based on their ability to deliver products which billions of people use and many are willing to sign contracts or make ongoing payments for.

Yes, there's some faith involved in assuming that the advertising market won't change overnight or that Google won't suddenly stop being able to compete effectively but that's orders of magnitude less than the level of faith needed to justify the current valuations, especially when the argument is not just that despite being unproven cryptocurrencies are certain to become mainstream but going further to say that a specific unproven implementation is going to win.