We used Mesos as our first container orchestration stack. It worked OK but Kubernetes came along and offered a one stop solution for everything. In Mesos you had to use separate projects for container management (Marathon), discoverability (Consul/HAPROXY). It seemed more geared to people that wanted to run their own stacks for such tasks. For a small to medium sized operation it was difficult to solve these issues where really they are issues everyone running a stack of containers has. This was in 2014 so it was early but k8s came along with everything we needed.