So the definition of success is that Go makes those people productive. If you give these fresh hires C++, now everything is on fire and even experienced people sent in to extinguish the flames end up just saying evacuate the entire site and let it burn itself out because that will be cheaper than diagnosing what's wrong.
This goal means some choices Go makes which I don't like seem more respectable. For example Go specifically warns you not to get clever. This is sound advice for a 22 year old new programmer who still probably thinks "Romeo and Juliet" is about true love, but it'd be very frustrating if you were trying to squeeze the last drops of performance juice out of a system. The answer from Google's point of view is that Go is the wrong language in that case and it's time to rewrite.
Also Go is mostly used externally, Google's key projects are all based on Java and C++, even Kubernetes would have stayed in Java if it wasn't for some Go folks joining the project and pushing for a rewrite.
From my discussions with employees at Google, the rationale for Go is to keep a large staff of promising CS graduates busy on dead-end projects (while preventing them from causing too much damage) until something takes off and they need to actually put some of that spare headcount to use.