Earlier quoted context omitted.
I think you're failing to include the firefox memory usage in that second example. the 200+MB memory of electron is because it includes the browser. Your 8MB file also needs firefox to run, so in a naked desktop environment the user first has to spin up 170MB+ of firefox before they can run your 8MB app.
But you do not need to have five full Firefox's running for using five web-app's. Another benefit of web apps, is that with some effort it can run everywhere, where as an app container like electron needs to have separate builds for each platform.
Mozilla had an experimental project called qbrt that was like electron but used the locally installed Firefox, exactly like you're describing. Hasn't been updated in quite a while though