k8s provides standardisation (technologically as well as business-wise), that's why is now lives at CNCF. Google wants everybody to use these as it allows for easier migration of these workloads on their cloud platform. k8s is at heart of their Anthos offering.
see https://www.nextplatform.com/2019/02/20/google-wants-cloud-s... for better explanation from Google's Urs Hölzle