Some articles, including this one give some arguments why docker is popular:
In a nutshell, here's what Docker can do for you: It can get more
applications running on the same hardware than other technologies; it
makes it easy for developers to quickly create ready-to-run
containered applications; and it makes managing and deploying
applications much easier. Put it all together and I can see why Docker
is riding the hype cycle as fast as I can recall ever seeing an
enterprise technology go.
Moreover, for once the reality is living up to the hype. Frankly, I
can't think of a single company of any size that's not at least
looking into moving their server applications to containers in general
and Docker in specific.
My personal view is that a tool could be successful if it will solve a (major) problem. For example, a half year ago I gave a presentation of docker in the company, the developers had some doubts until they experienced a issue that it was not possible to run all microservices on their local machine.
The same is applicable to the question:
Are NixOS and GuixSD the incoming Linux distros of DevOps?
It depends whether these distributions will solve a (huge) problem.