Eh, kitematic doesn't really do much in my experience, it's just a GUI over docker. It's just one of those things where they would have eventually made a GUI anyway, why not just try to grab the best one at the moment if they can?
It also doesn't feel like owning the ecosystem to me because someone else could (and I'd wager that a handful will) make a new GUI that becomes more popular than kitematic.
If you read between the lines "not trying to own the ecosystem" is just business talk for "we want ya'll to feel safe about buying into the thing we've built, so at the end of the road when we own the ecosystem, the checks go out to us". There's nothing wrong with that, as long as you understand what they mean.
Remember that Docker is a funded business, that has an obligation to its investors.
Docker is trying to be the center of the universe, just as SAP tries to do so beyond core applications with integration, monitoring, BI, systems, etc... Perhaps in the very long run this strategy could pay off, but I believe a lot of valuable companies will be created that focus on the gaps and really nail them in a focused manner.
I'm guessing the thinking was more along the lines of "hey, this is a cool tool that makes using docker easier. the crew who built it really love docker and have great expertise. let's bring them in and give them more resources to make docker even better."
It also doesn't feel like owning the ecosystem to me because someone else could (and I'd wager that a handful will) make a new GUI that becomes more popular than kitematic.