It's an awfully silly choice to use a managed service that only offers JavaScript and wasm if you don't want to use JavaScript and you care enough about performance that you're willing to accept the fairly meager benefits of wasm over JS. The real reason you'd choose wasm in this case is "I don't want to use JavaScript and I'm otherwise forced to use this service".
Back in the 1980s it was my greatest ambition to go on The Price Is Right and play Plinko. However all I could accomplish was making this cursed programming language instead. You'll love it.
Because the managed service you signed up to doesn't offer that to you. They like WebAssembly modules because it's a sandboxed runtime.