Redhat has a market cap of around 15 billion, that gives a rough idea of what kind of value Docker could build with a purely service based model for an open source product.
Redhat has a vast product suite now - they do a heck of a lot more than just RHEL, and a lot of it is "enterprise" stuff with juicy support contracts. Docker is a one-trick pony in comparison.
Wasn't RedHat a one trick pony at one point? I don't think it's insane to be that they'll be as successful as RedHat one day and it seems these investors would like to bet on it.
I think (with the exception of OpenShift), most of RH products are acquisitions. I can think of plenty of acquisitions Docker can make to take a similar path; Portainer, Kotena, some CI software (Drone, etc.) All that would kind of make Docker Inc a one-stop shop for startups (definitely) or whoever else wants everything from one company.
OpenShift is also an acquisition (OpenStack is not). [1]
What you say makes sense, but then Docker is also coming 10-12 years late to the game, and until it's profitable and has money in the bank it's hard to do many expensive acquisitions.
OpenShift started before Makara with a simple code base called "OpenShift Express". The code acquired with Makara was never used in the hosted service or what became the open source project, although some ideas crossed over.
OpenShift 3 (current) has no code in common with any of the older space. It was a totally new platform built on top of Kubernetes and docker.
A startup can get the same stack and much more from AWS, Azure or Google Cloud. If it should bet on one company, it should bet on the cloud it's already using.
