Google doesn't go in a direction, it goes in directions. Very large companies, especially companies like Google that have enormous computing needs, begin to worry about lots of things that us little guys don't directly worry about. Like: throughput/watt, total heat dissipation per cubic foot, electrical loss per backup, total throughput per cubic foot, etc. Companies don't do any one thing but have enough money to customer hardware to try out various combinations, min/max certain features, and use one company's hardware as a wedge to get better features/cost against other companies.
Undoubtedly, Google has a use case in mind, it's probably going to be five or more years before we hear why this particular hardware was of specific interest.