[int_19h]

We didn't do it with Java because JVM bytecode is very narrowly tailored to Java. For example, it doesn't have the notion of pointer arithmetic, for example, so you can forget about anything like C (one can emulate heap as a Java array and build the rest on top of that, of course - but only if performance doesn't matter).

On the other hand, wasm is low-level enough to handle C.

.NET / CLR was the previous attempt to do something like this, and it did have compilers for many different languages targeting it. But the downside there was that the runtime itself wasn't meaningfully portable for a very long time. If it were open and cross-platform from the get go, who knows, perhaps wasm would have been a CIL subset.