It's unclear to me why they needed to compile Rust to WebAssembly to write a website. It looks like iroh has a JavaScript API:

https://docs.iroh.computer/languages/javascript

Edit: actually, that's a Node.js-specific API. For browsers, it seems like they should have a platform-independent JavaScript/TypeScript API that includes a WebAssembly file (if needed) instead of expecting you to compile WebAssembly yourself.

Not touching JavaScript might be a reason enough. (Though I bet it has a Typescript API, and Typescript is great.)