WASM uses the current JS/VM environments to leverage its existing infrastructure (i.e. low-level abstraction and security). In practice it is a pre-optimized bytecode that only relies on JS primitives, so it does not need dynamic typing features or GC, i.e. the slowest and least safe parts of JS. Which means that anything compiled to WASM is "near-native" in terms of performance, making the use of a separate VM unnecessary.