The target audience is developers who are efficient at generating HTML server-side using an MVC framework, a template engine, whatever they're comfortable with. Instead of building a JSON API and a JavaScript layer to consume it, you just return HTML fragments from your existing routes.

µJS handles the AJAX call and swaps the fragment in the DOM. No JavaScript to write, no state to manage client-side. jQuery is more powerful and flexible, but that flexibility comes with complexity: you have to write the fetch call, handle the response, find the right DOM node, update it.

µJS does all of that declaratively via HTML attributes. It's not for every use case — highly interactive apps (think Google Maps or a rich text editor) still need proper JavaScript. But for the vast majority of web pages, server-rendered HTML fragments are simpler, faster to develop, and easier to maintain.