Reusable components were already there using jquery plugins. Everyone used them and they were easy to use and easy to install. They were deployed as a single file, with optional CSS.
Try writing a reusable component now. You have to target all major frameworks and tooling.
I think you may be conflating components and good old fashioned libraries. You can certainly make a component into a library but that's not their main use case. Their main use-case is for organization and reusability within a singular codebase.
I write reusable components all the time inside my codebases. I never have to target anything except the stack I'm using for my project.
Components as jQuery plugins aren’t encapsulated or easily composable. What do you do if two plugins used the same namespace or class names? How would you put one component inside another?
Reusable components were already there using jquery plugins. Everyone used them and they were easy to use and easy to install. They were deployed as a single file, with optional CSS.
Try writing a reusable component now. You have to target all major frameworks and tooling.