There's one huge problem WASM solves compared to other existing solutions: memory safety. Instead of running untrusted computational code in a separate process,

There's one huge problem WASM solves compared to other existing solutions: memory safety. Instead of running untrusted computational code in a separate process, you can run it all in a single process since WASM linear memory has bounds checking. It also combines this with extremely constrained API access giving you a way to sandbox code with almost native performance. Besides memory checking, there are much fewer nasty things a process can do in terms of control flow since executable memory (procedures) do not exist in linear memory. It supports function pointers via a separate table system (kind of like having a separate address space for executable memory). All of this is in place so if a WASM module crashes, it doesn't take down whatever process it's running in.