Because Vite emphasizes "Optimized build" in their marketing

Slower builds might make developers more thoughtful of the bloat, but I still think it’s tangential.

That said, how does Nue compare to, say, Svelte?

I'm not sure if I got this correctly, but it seems like you're misunderstanding what Vite actually is or does.

For having built what is essentially a bundler, I would've guessed you were more familiar with what it does, or, perhaps even have used it to build your tool.

Vite can bundle framework-less html files. It can create an SPA without any JS faff. You just have to point it to the right direction. When you instantiate a Vite app, you have to make the conscious decision to use React under the hood.

As for Nue, I think it's a cool idea, but I don't see what it does that I couldn't do with Astro, which has way larger community support and can work with pretty much all JS frameworks OOB.

BTW, I think it's really disingenuous to compare a React SPA bundle with an SSG output. You have essentially no functionality for handling state mutations beside events. You could achieve a much better middle ground by using a compiled framework like Svelte or Solid.