Jokes aside, why are you comparing these two very different virtual machines? WASM is a general purpose VM, JVM is not. For example, you won’t find a Rust JVM target any time soon. (Not to suggest that the JVM is strictly limited to Java, it isn’t obviously, but it is not nearly as suited to being a target for lower level languages. Also, the security model is very different.)
Wasm is a good idea but it's going to need to reimplement a lot of existing code (optimizing + jit).
Doable and maybe it will convince people to do what has been a great idea first widely deployed by Java: compiled language in an abstract machine.
Still, since the Java platform didn’t capture this use case of a general purpose abstract machine, it makes a whole lot of sense to develop something like WASM. It’s a much more neutral platform to build on.
In particular we actually don’t need to go through all of the things Java went through; we have a wealth of knowledge about what things work and what things don’t work so well. Yes, its a new JIT, but not that new: from my understanding typically the JavaScript JIT machinery is reused for the WASM JIT in browsers.
The fact that it was bundled as a browser plugin, mostly.
Where the hell did you get that idea? WASM can be used as just another frontend for javascript JIT engines like V8 or SpiderMonkey.