But they also figured out that making their free-as-in-beer tools also free-as-in-freedom open source, they'd lift all clouds and not just their own.

As the dominant player, Amazon loses from anything that reduces vendor lock-in. That's why precious little of Amazon's cloud tooling is released on Github.

With Kubernetes, Google made the the opposite calculation. As a challenger, it's to Google's benefit to open-source cloud tooling like Kubernetes. Even though their competitors benefit, Google benefits more from standardized tools that reduce switching costs.