I'm not very qualified to speak on the subject, but Svelte had (last I checked) the feature of not having a VDOM, meaning I was able to use generic JS libraries with it that did not require a implementation that was Svelte-only, as is the case with many such React and Vue libraries.
Personally, I like to stay as close to web standards as possible, instead of tying myself to specific implementations of specific addons for specific frameworks.
I was referring to how React and Vue have a whole internal virtual implementation of the DOM which prevents many vanilla JS libraries from working with them.
Svelte is built to not require this abstraction (VDOM), which increases the likelihood that it will work with other JS libraries out of the box.
Personally, I like to stay as close to web standards as possible, instead of tying myself to specific implementations of specific addons for specific frameworks.