"A new report from Protocol today details that Apple has gone on a cloud computing hiring spree over the last few months... Michael Crosby, one of a handful of ex-Docker engineers to join Apple this year. Michael is who we can thank for containers as they exist today. He was the powerhouse engineer behind all of it, said a former colleague who asked to remain anonymous."
We can thank the linux kernel developers for implementing namespaces and overlayfs.
And we can thank predecessor systems like BSD jails, Solaris zones, as well as Virtuozzo/openVZ and lxc as previous container systems on linux.
Docker's main improvements over lxc, as I understand it, were adding a layered, immutable image format (vs. repurposing existing VM image formats) and a "free" public image repository.
But the userspace implementation isn't exactly rocket science, which is why we periodically see HN posts of tiny systems that can run docker images.