Yep, and yet, what a Californian knows is not what a Global 2000 does. We had a new Swarm user last quarter and another Global 2000 doing Mesos, both through their central IT. This month, a team trying us out with their new experimental Hadoop cluster.
I have seen the container implementations for hundreds of companies and I'm just pointing general out trends.
Swarm is used quite a bit on day one but generally phased out long before production. Mesos still has traction on very large deployments but fewer new initiatives start there these days --although there certainly still is investment here.
What is most interesting to me is that the longer a company has been using containers the more likely you see Mesos because three or four years ago kube was not the first choice like it is today.
... And those aren't ECS. I'm not saying ECS is unpopular, just what tech co's do 90% of the time is't what Global 2000 does 90% of the time, so know your customer.
Very few companies our building their own clusters (sure they are out there, mostly banks, financials and gov)