Earlier quoted context omitted.
Why? Electron apps still have to be packaged for Linux. And cross platform apps can be written in Qt or Java too. Doesn't seem like Electron is the thing making the difference here.
Have you actually written a large scale cross platform app for Linux and Windows? Sure, Qt components will show up on both platforms. But to get them to show up the same tends to be an incredible headache, especially if custom styling is applied.
It was quite productive and straightforward. That said, Java likes to use as much RAM as it can get even if it could release a lot back to the OS. It looks at it, sees it's free and thinks "I might as well take that".