The difference might be HTTP vs HTTPS. On a Pi the extra CPU load to properly encrypt the HTTPS stream is probably significant.

This isn’t about replacing javascript, this compiles something that looks a bit like Python to C and then to WASM. Which browsers can run natively these days. But you can do that with any source language if there’s a compiler for it, type safe or not. You can compile Rust to WASM too for example. So nothing’s getting replaced, these are just additional tools for Web developers.