I assume it's various things. I think for me at least React and other SPA frameworks fixed a different problem I think most could agree with: reusable web components. I don't think anything like that existed before on the front-end, and by making it a front-end specific solution, it is fluid enough to transcend back-end languages, but then it became bloated.

I love back-end work and I prefer front-end code to be as vanilla as can be. If I want a UI I pull in Bootstrap or some CSS framework because I'm not a designer.