One could write a js-less DOM impl I think.. neither Chrome nor Firefox itself is written in js unlike big parts of Linux that are indeed written in C. Explorer shipped with vbscript as a language that can manipulate the DOM.
The really big issue in this case is network effect, which is why I hope something can come out from the momentum building behind WASM.
One couldn't, because you'd need to standardize a JS-less DOM, which requires one to persuade Apple, Google, Microsoft, and Mozilla to agree on a new standard for a JS-less DOM API.
The DOM API is currently defined as a JS API, including JS strings, JS objects + properties, JS Exceptions, JS Promises, JS garbage collection, and on and on and on.
The effort to get all the browsers to agree to standardize a new JS-less DOM API would take years; none of the browser vendors even want to begin that conversation today.
The issue is that many modern DOM APIs assume js semantics and types (eg promises, iterables, etc) so you need to "reimplement" some js semanthic in wasm; sorta like how apple added a few custom instructions on the M1 chip specifically for the type of floating point operation required by js.
The really big issue in this case is network effect, which is why I hope something can come out from the momentum building behind WASM.