The problem with java is the language and how it works itself, and not the byte code idea.
I say that as a few things do that and .net, java and wasm are the first that jump to mind.
Hell, pure technically any programming language that is not asm does that :')
My problem is java itself, not its byte code. Wasm as advantage, imo, is that its not stuck to a single language like java is. .net blazor can build to wasm, but you could also use c++ to compile wasm applications :)
I'm not sure why the WASM creator(s) didn't take advantage of the existing java bytecode and JVM instead of reimplementing it. Might've sped up its adoption. Doesn't matter to me though, as long as JS stops being the #1 in web development.
Why would they? WASM is Web-Assembly, so Assembly is a lower level language than Java.
You can use C# WASM through Blazor, and Java WASM though JWebAssembly. WASM as core is supposed to be language agnostic. So If you want a JVM in WASM you can build it on top of it