By far the most popular solution to running containers on Linux (at least at the time of writing) is Docker.
Starting out as a way for Docker Inc. (then dotCloud) to better utilize containers in their PaaS (Platform-as-a-Service) company, Docker quickly gained traction in the open source world and was soon seen as the future of computing in a lot of circles (the cynical sysadmins generally came after the developers got wind of it).
Because it's effectively a simple way to use already-present kernel features, and includes the Docker Hub for people to both upload and download pre-built images, it made containers easy.
Soon, people were containerizing everything, from Firefox, to Nginx, to entire distributions, just because.
I firmly believe that the ease with which Docker made it possible to upload and download their images contributed to its success....