Docker made containers easy and effective. Solaris zones were not as good as Docker is, BSD jails are/were not as good or easy to use as Docker is. Popularity has nothing to do with it, except that the popularity is an indication of the fact that Docker was revolutionary in the way it made these technologies accessible to a very large professional audience.
Docker was not created in isolation, it was inspired by jails and zones and all the fancy new features that were added to the linux kernel at the time.
Using just the words FROM, ADD and CMD, you can make a container definition that effectively isolates a runtime for just about any application in a 3 lines. Beyond the couple simple keywords all you need to have is absolutely basic linux knowledge, the level you can teach any developer in an afternoon.
There's no need to pollute that developers mind with any other system administration garbage. Nothing about networking, policies, filesystems, whatever. Just basic bash and a couple keywords.
Then when you want to go to production, you just hand the shit your developers wrote over to a professional system administrator and they'll make it run perfect at any scale. It's magic. Before Docker the world was darkness and bullshit, and after Docker the world was drenched in light and all that is good.
The fact that it's 2022 and there's still people that are going "hur-dur Solaris zones, BSD jails amiright" as if any of those technologies have any relevance is ridiculous.
Docker is technologically excellent.