Because electron consumes CPU cycles and RAM like there's no tomorrow.

Which is the very reason alternatives to Electron, that are more lightweight exist, of course.

I suspect a parse error somewhere.

Indeed, the person you're replying may have experienced a parse error, but this isn't the same person as the one who claimed it's an oxymoron.

Maybe they made that claim because an alternative to Electron probably still uses HTML5 and JavaScript, and HTML5 and JavaScript are huge so it's hard to believe such a thing could be lightweight.

Anyone who says "JavaScript" is "huge" needs to be asked to both qualify and then substantiate the claim (along with the implicit suggestion that they have any idea what they're talking about, instead of just trying to participate in the pile-on with cheap remarks).

There's javascript runtimes for MCUs with <16MB of RAM (no, they are not the same as V8 in Chrome/Node/Electron, but that's the point: large range with many possible solution sizes)