Firefox lost that market a long time ago. Electron won because chromium is modular, the tech can be re-used for other purposes. Firefox lost because it's a monolith you can't use in your projects.

WPA's and webviews are non solutions. You can't have web sandboxing and also the privileges a desktop app needs. Wasm is a failed experiment that did not result in the performance improvements promised. You still need to compile C++ modules for all kinds of things.