The reason, apparently is because Google can no longer sit comfortably behind the scene to watch others play the catch up. Previously Google do not care, because they dont want to share internal Cloud with you. Now they need the profit from Cloud. Google needs to show that it is still the leader. Previously, Google does not need to show anything and all believe they are the leader. After missing the Cloud movement in the past years, Google's reputation has been tainted, and they have to show hard proofs.
For example, when choosing cloud providers, AWS is still the clear no1. People probably still believe that GCP is better than AWS. But GCP does not have the proof. However, if Google somehow can catch up and beat AWS in a decisive manner overnight, then Google still does not need to share anything; and no one will question that Google is the leader. Apparently, Google is not able to do that. It might be that Google is not focused enough. But Google cannot let people have the other impression "Google's technologies might not be as good as we thought" grow in people's mind.
Can you imagine what would happen if Google started the Cloud thingy at the same time as AWS? Then Google certainly do not need to share a damn thing with outside world...