Sure but in WASM, the browser's environment is taking responsibility for many OS concerns (graphics, IO, 3D, hardware). In a Docker image, all that logic needs to be bundled in libraries as you'll only get to "reuse" the hosts' kernel.

A 'fairer' comparison would be a optimized and compiled binary that dynamically links to the OS versus a WASM product (would be kilobytes-megabytes).

Or having the WASM app in a Chromium browser in Docker (would be gigabytes).