When this decision was made years ago, it was very NIH / I want to make a language because it sounds cool. It does seem this was toned down quite a bit from those days to something that is yaml with curl braces, still reeks of hackish when you put --- at the top just so people don't think it is json. They could have just adopted json5 by the looks of it, alas NIH is pervasive
I'm certainly unlikely to adopt a config language just for k8s. I don't even directly interact with k8s yaml these days, CUE / Helm are my interfaces