[freedomben]

IMHO, it was the whole package: One tool that could configure and wrangle all the various kernel namespaces in order to make containers work.

They also benefited significantly from the splash they made and the tech excitement factor. I still run into people in my consulting work that are fairly new to containers, but brand recognition on Docker is through the roof. Everybody has heard of them even if they don't know what it can do for them.