They had started this move months before Microsoft purchased Github. If you read the linked article one of the biggest reasons is that the GCP implementation o

They had started this move months before Microsoft purchased Github. If you read the linked article one of the biggest reasons is that the GCP implementation of kubernetes and better integration with their CDN they'll be getting a significant performance boost. It's taken this long since they've had to make infrastructure changes along with some code changes to get it better supporting the deployment there.