Java bytecode and CLR are not great targets for compiling C++ to and implementing performant VMs for them is much more difficult than a WASM JIT. The WASM FAQ

Java bytecode and CLR are not great targets for compiling C++ to and implementing performant VMs for them is much more difficult than a WASM JIT. The WASM FAQ has an entry about LLVM IR: https://github.com/WebAssembly/design/blob/master/FAQ.md#why-not-just-use-llvm-bitcode-as-a-binary-format https://github.com/WebAssembly/design/blob/master/FAQ.md#why...