Why did Docker take off, but Nspawn didn't?

Topic title. Docker is so ubiquitous these days in the public dev space that it's almost unreal to me. It seems like a good 70% of FOSS requires it - and with it all the loquaciousness of YAML and Docker compose. I use it, because I have to.


But whatever happened to the humble systemd-nspawn container? It gives you roughly comparable size to most Docker containers, is (IMO) a heck of a lot easier to configure and run, is portable across systemd systems everywhere, and has been a native part of the Linux ecosystem for over a decade. Was it just Kubernetes coming out the gate swinging that caused Docker to take over the world? I still prefer nspawn, and use "full stack" containers for deployments of things like edge ingress nodes because its fast, simple, intuitive, and hard to screw up.

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