Svelte is actually quite a bit different. Quoting a random section from their docs
"[Svelte is a] compiler that knows at build time how things could change in your app, rather than waiting to do the work at run time"
My point being there is a large amount of compile time code transformation at build time. The run time is not so much a framework as a library like libc. In Svelte when you update state there is no virtual dom, dom diffing, fibers, or anything. It would have been compiled into a direct dom update of anything depending on it. It's no longer a Svelte app just vanillajs. There are some details or course but it's a different paradigm than to react or other modern UI frameworks.
"[Svelte is a] compiler that knows at build time how things could change in your app, rather than waiting to do the work at run time"
My point being there is a large amount of compile time code transformation at build time. The run time is not so much a framework as a library like libc. In Svelte when you update state there is no virtual dom, dom diffing, fibers, or anything. It would have been compiled into a direct dom update of anything depending on it. It's no longer a Svelte app just vanillajs. There are some details or course but it's a different paradigm than to react or other modern UI frameworks.