Wasm "solves" running your application in a shared environment. i.e not your machine but say a cloudflare machine, that has to run dozens of applications like yours.

Without wasm, the unit of containerization for them is operating system process. Each process spins up a jvm that runs your app/backend API.

With wasm, the unit of containerization is the exact functions of your backend API. So they can fit more "containers" on a single machine, compared to docker. And that brings faster startups etc..