Yeah, I think people are overthinking it. The real reason is that if you do a superficial investigation you will quickly come back with the impression that k8s is near universally supported across cloud vendors and gives an appearance of providing a portable solution where otherwise the only alternative would be vendor lock-in. It makes it a no-brainer for anybody starting out with a new cloud deployment.
1. It's simple to get started with, but complex enough to tweak to your needs in respect to simplicity of deployment, scaling and resource definition.
2. It's appealingly cloud-agnostic just at the time where multiple cloud providers are all becoming viable and competitive.
I think it's more #2 and #1; as always, timing is everything.