Kubernetes beat Mesos/Marathon, which is written on Scala. I don't think that's just a coincidence.
Failure of a project's adoption usually traces back to people and management, not technology.
I think that has more to do with the fact the k8s devs had a complete implementation of the the same product (Google's Borg) as reference. Mesos/Marathon only had a couple 10 page journal articles to look at and a ton of on the ground decisions to make and quantify the choices of.
https://changelog.com/gotime/105
https://archive.fosdem.org/2019/schedule/event/kubernetesclu...