I said a big reason, not the only reason.

Besides, Mesos wasn't a good alternative for most companies, so saying "they could have chosen it instead" is a bit theoretical. Mesos was ambitious, but that made it less suitable for a plug & play system that fit easily into existing corporate systems, which had already adopted containers heavily.[] Another reason for Kubernetes' popularity is it didn't try to be a big leap forward the way Mesos did.

[]The Marathon container support for Mesos was released about a year after Kubernetes, but if you were going to set up a system for distributed orchestration of containers, it didn't make much sense to bring Mesos along for the ride. There's a reason Mesos is in Apache heaven now (the Attic.)