Once upon a time there were programmers.
Then there were systems programmers and application programmers. Systems programmers wrote operating systems and utilities for them. App programmers wrote apps. There was a lot of crossover.
Then there were operators, systems programmers and application programmers. Operator was a junior position who did physical things (mount tapes, plug in cables) and ran commands to do things on the systems. They usually moved up to being...
Systems administrators, who did some programming in service to the systems, but not too much. The more senior a sysadmin was, the more time they spent programming and the less time they spent doing physical things... unless they wanted to do that.
Sysadmins started to specialize. People who configured switches and routers and talked to telephone companies became "network engineers". People who spent time working on firewalls and security policies and thinking about that became "security engineers". Junior people who read scripts to end users became the helpdesk. And so forth.
Then we noticed that a bunch of people were doing things manually when they should be automated. This was especially bad in places where there were no senior sysadmins or systems programmers. But we did have the internet, and senior sysadmins got together and started writing tools to make their lives easier: infrastructure automation.
You probably know the story from there, but I'll wrap up with one more important point: you know how when writing a business application you need to have a subject matter expert who actually knows what they are doing? Operations is exactly the same way. All the automation in the world won't help you if you don't have someone around who knows what they are doing. Some people can outsource this to "the cloud", but not everyone.