Compiling Rust to WASI

The core use cases of WASI have nothing to do with browsers. Yes, though: Java itself--without applets--also solves mostly the same problem.

I prefer WASM to the JVM

I think the main difference between WASM and JVM is that WASM was designed as a generic compilation target for all kinds of existing languages like C or Swift, while JVM is designed to specifically run Java bytecode with the features that Java-based languages support.